Types of research design, sampling methods & data collection

Types of research design,sampling methods&data collection
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Types of Research design
Sampling methods and Data
collection
Bipin Koirala
Maharajgunj Medical Campus
Institute of Medicine

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Sampling is an act, process, or technique of selecting a suitable sample,or a representative part of a
population for the purpose of determining parameters or characteristics of the whole population.
Some basic terminologies:
Sample designisa definiteplanforobtainingasample fromagivenpopulation.Itreferstothe technique
or the procedure the researcher would adopt in selecting items for the sample.
Sampling errors are the random variations in the sample estimates around the true population
parameters. Since they occur randomly and are equally likely to be in either direction, their nature
happensto be of compensatorytype andthe expectedvalue of sucherrorshappenstobe equal to zero.
Sampling error decreases with the increase in the size of the sample, and it happens to be of a smaller
magnitude in case of homogeneous population.
The selected respondents constitute what is technically called a ‘sample’ (Subset of Population under
study) and the selection process is called sampling technique.
Population: Groups of individuals under study
Target Population: Study population from which sample is drawn.
Sampling frame: Listing of members of the accessible population from which
sample is drawn.
Sample size: Number of selected units of population.
Census: When data is collected from each member of the population.
There are different types of sample designs basedon two factors viz., the representation basis and the
elementselectiontechnique.Onthe representationbasis,the sample maybe probabilitysamplingorit
may be non-probability sampling. Probability sampling is based on the concept of random selection,
whereasnon-probabilitysamplingis‘non-random’sampling.Onelementselectionbasis,the samplemay

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be eitherunrestrictedorrestricted.Wheneachsampleelementisdrawnindividuallyfromthe population
at large,thenthe sample sodrawnisknownas‘unrestrictedsample’,whereasall otherformsof sampling
are covered under the term ‘restricted sampling’.
Thus,sample designsare basicallyof twotypes’viz.Non-probabilitysamplingandProbabilitysampling.
Characteristics of a good sample design:
(a) Sample design must result in a truly representative sample.
(b) Sample design must be such which results in a small sampling error.
(c) Sample design must be viable in the context of funds available for the research study.
(d) Sample design must be such so that systematic bias can be controlled in a better way.
(e) Sample shouldbe suchthatthe resultsof the sample studycanbe applied,ingeneral,forthe universe
with a reasonable level of confidence.
Types of sampling techniques:
S.N Probability sampling Non probability sampling
1. Simple random sampling Purposive sampling
2. Systematic sampling Quota sampling
3. Stratified sampling Convenience sampling
4. Cluster sampling (Area sampling) Snowball sampling
5. Multistage sampling

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Non probability sampling:
Non-probability sampling is that sampling procedure which does not afford any basis for estimatingthe
probability that each item in the population has of being included in the sample. It is also known by
different names such as deliberate sampling, purposive sampling and judgement sampling. In other
words, under non-probability sampling the organizers of the inquiry purposively choose the particular
unitsof the universe forconstitutingasample onthe basisthat the small mass that theyso selectoutof
a huge one will be typical or representative of the whole.
For example:
If economic conditions of people living in a state are to be studied, a few towns and villages may be
purposively selected forintensivestudy on theprinciplethatthey can berepresentativeof theentire state.
Thus, the judgement of the organizers of the study plays an important part in this sampling design so
called judgmental sampling. In such a design, personal element has a great chance of entering into the
selection of the sample. The investigator may select a sample which shall yield results favorable to his
pointof viewandif that happens,the entire inquirymaygetvitiated.Thus,there isalwaysthe dangerof
bias entering into this type of sampling technique. But in the investigators are impartial, work without
bias and have the necessary experience so as to take sound judgement, the results obtained from an
analysisof deliberatelyselectedsamplemaybe tolerablyreliable. Itisusuallycheaper,usedmostlywhen
the sampling frame is not available & used when random sampling is not feasible.
1. Purposive sampling
Itisalsocalledas Judgmental sampling.Researcherwillchoosethe sample basedonwhotheythinkwould
be appropriate for the study and the selection is done based upon characteristics of population &
objective of the study.
Thissamplingmethodislesscostly,lesstimeconsuming, alsoavoidsirrelevantitemsenteringthe sample.
Sampling error in this type of sampling cannot be estimated and the element of bias, great or small, is
alwaysthere.Assuch thissamplingdesigninrarelyadoptedinlarge inquiresof importance.However, in
small inquiries and researches by individuals, this design may be adopted because of the relative
advantage of time and money inherent in this method of sampling.
Example:
a. The researchercollects the respondentsof age20-30 yearsmale clinicians in eye hospitalto study
their status of Binocular single vision.
b. To study the Computer Vision Syndrome in
management students, only the students
studying management stream of particular
institute are included in the sample.
2. Convenience sampling
This sampling method is well known as accidental
samplingorhaphazardsampling.Sample selectionis

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done on the basis of convenience and readily availability. This sampling technique is oftenused in pilot
study.Alsoitsavesbothtime and money. Inthissamplingmethodthereisnoevidence of representation
of populationonthe sample alsoit is difficulttogeneralize the populationfromsamplingresults.Beside
this the sample may be over selected or under selected which will increase the sampling errors.
Example:
a. A reporter can take views of people in certain issues at street
b. In clinical practice, use of clients who are available to us as our sample.
c. Enrolling patient attending orthoptics
roomwithof complain headacheasour
sample.
3. Quota Sampling:
Quota sampling is also an example of non-
probability sampling. Under quota sampling
populationisfirstsegmentedintomutuallyexclusive subgroupsjust as in stratifiedsampling.So,during
quota samplingthe interviewersare simplygivenquotastobe filledfromthe differentstrata,withsome
restrictionsonhowthey are to be filled.Inotherwords,the actual selectionof the itemsforthe sample
islefttothe interviewer’sdiscretioni.e. conveniencesamplingisusedtoselectthe subjectsorunitsfrom
each segment based on a specific proportion.
Thistype of samplingisveryconvenient,canbe done inshortperiodandisrelativelyinexpensive.Butthe
selection of sample is nonrandom so the samples may be biased.
Example:
a. A Sample of 100 females or 100 males between ages of 25-30.
b. Let’s say the researcher is investigating views on the death penalty and wants to make sure
minorities are included in the survey.Thepopulation may consistof 3% Native Americansbutthe
researched changes the quota to 5% to ensure the views of Native Americans are included. The
inclusion of certain minorities has come at the expense of a truly representative sample.
4. Snowball sampling:
Snowball sampling is well known as chain sampling, chain referral sampling or simply referral sampling.
Thissamplingmethodisusedwhendesiredsamplingcharacteristicsisrare innaturesosample generation
relies on the referral of initial subject to additional
subjects. This technique aims at finding the hidden
subject. It is easier to conduct and information could be
obtained within short period of time hence saves both
time and money. But the selection of sample is
nonrandom so the samples may be biased.

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Example :
a. Criminal study in organized crime
b. Drug abuse study,
c. Prostitution study
d. Can be used to identify experts in a
certain field such as medicine
Probability sampling
Probabilitysamplingisalsoknownas‘randomsampling’or‘chance sampling’.Underthissamplingdesign,
everyitemof the universehasanequal chance of inclusionin the sample.Itis,sotosay,alotterymethod
in which individual units are picked up from the whole group not deliberately but by some mechanical
process. Here it is blind chance alone that determines whether one item or the other is selected.The
resultsobtainedfromprobabilityorrandom sampling can be assuredin termsof probabilityi.e.,we can
measure the errors of estimationorthe significance of resultsobtainedfroma randomsample,and this
fact brings out the superiority of random sampling design over the deliberate sampling design. Random
samplingensures the lawof Statistical Regularity whichstatesthatif onan average the sample chosenis
a random one, the sample will have the same compositionandcharacteristicsasthe universe.Thisisthe
reasonwhyrandomsamplingisconsidered asthe besttechnique of selecting a representative sample.
1. Simple Random Sampling:
Simple random sampling is used when the sample size is small
and the population under study has similar characteristics and
readilyavailable.Inthismethodeachmemberof populationgets
equal chance of beingchosenbyeitherlotterymethodorrandom
number table.
How to select a Random Sample?
Withregard to the questionof howtotake a random sample inactual practice,we could,insimple cases
like the one above,write eachof the possible samplesona slipof paper, mix these slipsthoroughlyina
containerand then draw as a lotteryeitherblindfoldedorby rotating
a drum or by any other similar device. Such a procedure is obviously
impractical, if not altogether impossible in complex problems of
sampling. In fact, the practical utility of such a method is very much
limited.Fortunately,wecantake arandomsampleinarelativelyeasier
way without taking the trouble of enlisting all possible samples on
paper-slipsasexplainedabove.Insteadof this,we canwrite the name

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of each elementof a finite populationona slipof paper, putthe slipsof paper so preparedinto a box or
a bag and mix them thoroughly and then draw (without looking) the required number of slips for the
sample one after the other without replacement. In doing so we must make sure that in successive
drawingseach of the remainingelementsof the populationhasthe same chance of beingselected.This
procedure will also result in the same probability for each possible sample.
Example:
We have a finite population of 6 elements and we want to select a sample of size 3, the probability of
drawing any one element for our sample in the first draw is 3/6, the probability of drawing one more
element in the second draw is 2/5, (the first element drawn is not replaced) and similarly the probability
of drawing one more element in the third draw is 1/4. Since these draws are independent, the joint
probabilityof thethreeelementswhich constituteoursampleistheproductof theirindividualprobabilities
and this works out to 3/6 × 2/5 × 1/4 = 1/20.
Simple randomsamplingisa scientificmethod of samplingwhichisaccessible atlimitedcost, and labor.
It is more ideal for statisticpurpose and allowseasiercalculationof meanand variance.But it has some
demeritstooasitneedsacomplete updatedlistof unitsof population.Alsothe numberingof population
is tediousandtime consuming.Likewise itmightbe too expensive toconductif sample mayis scattered
over a wide area.
2. Complex Random sampling designs
Such designs may as well be called ‘mixedsampling designs’ for many of such designs may represent a
combination of probabilityand non-probabilitysampling procedures in selecting a sample.Some of the
popular complex random sampling designs are as follows:
a. Systematic random sampling:
The mostpractical wayof samplingistoselectevery N thitemonalistandsamplingof thistype isknown
as systematic sampling. In this methodthe targeted population is arranged according to some ordering
scheme and then selection of elements is done at regular intervals through ordered list.
Examples:
a. If a 4 percent sampleis desired,thefirstitem would beselected randomly
from the first twenty-five and thereafter every 25th item would
automatically beincluded in thesample.Thus,in systematicsampling only
the first unit is selected randomly and the remaining units of the sample
are selected at fixed interval.
b. If we want 20 sample from the 100 population, and if their name is
arranged on alphabetical order, divide 100 by 20 we will get 5. Here 5 is
the sampling interval.Now, randomly selectno between 1 and 5 suppose

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4 then, starting point will be the 4th person in list next 9 then so on at an interval of 5.
Although a systematic sample is not a random sample in the strict sense of the term, but it is often
consideredreasonable totreat systematicsample asif it were random sample. Systematicsamplinghas
certain plus points. It can be taken as an improvement over a simple random sample in as much as the
systematicsample isspreadmore evenlyoverthe entire population. Itisaneasierandless costly method
of samplingandcanbe convenientlyusedevenincase of large populations.Butthere are certaindangers
too in using this type of sampling. If there is a hidden periodicityin the population, systematic sampling
will prove tobe aninefficientmethodof sampling.Alsotheupdatedlistof populationmaynotbe available
in every instances.
b. Stratified random sampling
Stratified random sampling technique is used when the population under study is non homogenous.
Stratification is the processof grouping members of populationinto relatively homogeneoussubgroups
before sampling.Inthissamplingpopulationunderstudyisfirstdividedintohomogenousgrouporclasses
calledstrata and thensample isdrawnfrom eachstratum at randomin proportiontoits size.Subgroups
thusformedare basedonsomepredeterminedcriteriasuchasgeographiclocation,age,sex,socialstatus,
occupation.that the strata be formedon the basis of commoncharacteristic(s) of the itemsto be put in
each stratum.This meansthat variousstrata be formedin such a wayas to ensure elementsbeingmost
homogeneous within each stratum and most heterogeneous between the different strata. Thus, strata
are purposively formed and are usually based on past
experience and personal judgement of the researcher. One
should always remember that careful consideration of the
relationshipbetweenthe characteristicsof the populationand
the characteristicstobe estimatedare normallyusedtodefine
the strata. At times, pilot study may be conducted for
determining a more appropriate and efficient stratification
plan.We can do so by takingsmall samplesof equal size from
each of the proposedstrataand thenexaminingthe variances
within and among the possible stratifications, we can decide an appropriate stratification plan for our
inquiry. For selection of items for the sample from each stratum, resorted to is that of simple random
sampling.Systematicsamplingcanbe usedif it is consideredmore appropriate incertainsituations. This
sampling method thus improvesthe accuracy of estimation. It also allows the use of different sampling
technique for different subpopulation. This method helps to select sample from defined areas, classes,
ages,sexes,etcwhichrepresenttoall strataof society orpopulation. Butinthismethodit canbe difficult
to selectrelevantstratificationvariables alsoitmightbe expensive toimplement.Itmaycreate problems
if strata not clearly defined which makes analysis quiet complicated.

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c. Cluster sampling
Whentotal area of interesthappenstobe a bigone,a convenientwayinwhicha sample can be takenis
to divide the areaintoa numberof smallernon-overlappingareasandthentorandomlyselectanumber
of these smallerareas(usuallycalledclusters),withthe ultimate sample consistingof all (or samplesof)
units in these small areas or clusters. This method of saampling is also called as two stage sampling. In
this method total population divided into clusters such as villages, wards, hospitals, schools.
Clustersampling,nodoubt,reducescost by concentratingsurveysinselectedclusters.Butcertainlyitis
lessprecise thanrandomsampling. Clustersmaynotbe representativeof whole population andanalysis
can be more complicated.similarly there is chance of high sampling error.
Area sampling: If clusters happen to be some geographic subdivisions, in that case cluster sampling is
better known as area sampling.
Example:
a. Cluster sampling is used to estimate high mortalities in cases such as wars, famines and natural
disasters.
b. A businessownerisinclined towardsexploring thestatisticalperformanceof herplantswhich are
spread acrossvariouspartsof the india . Considering thenumberof plants,numberof employees
per plant and work done from each plant, single-stage sampling would be time and cost
consuming.This is when she decides to conducttwo-stagesampling.Theowner creates samples
of employees belonging to different plants to form clusters and then divides it into thsize or
operation statusof the plant.A two-levelcluster sampling wasformed on which other clustering
techniques like simple random sampling were applied to proceed with the calculations.

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d. Multi Stage sampling
Multi-stage samplingisafurtherdevelopmentof the principleof clustersampling.It isacomplex formof
clustersampling.Itisusedinlarge countrysurveys. Populationisregardedasmadeof anumberof primary
units each of which further composed of number of secondary units. There are two advantages of this
samplingdesign.Itiseasierto administerthanmostsingle stage designsmainlybecause of the fact that
samplingframe undermulti-stage samplingisdevelopedinpartial units.A large numberof units can be
sampledfora givencostundermultistage samplingbecause of sequential clustering,whereasthisisnot
possible in most of the simple designs. Analysis more complictaed in multi stage sampling.
Example :
a. we want to investigate the working efficiency of private banks in nepal and we want to take a
sampleof fewbanksforthis purpose.Thefirst stage is to select large primary sampling unitsuch
as states in a country. Then we may select certain districts and interview all banks in the chosen
districts.This would representa two-stagesampling designwith theultimatesampling unitsbeing
clustersof districts. If instead of taking a censusof all bankswithin theselected districts, weselect
certain towns and interview all banks in the chosen towns. This would represent a three-stage
sampling design.If instead of taking a censusof all bankswithin theselected towns,werandomly
samplebanksfromeach selected town,then it is a caseof using a four-stagesampling plan.If we
select randomly atallstages,wewillhavewhatisknown as‘multi-stagerandomsampling design’
b. To study the practice of emergency physician doctors , the researchermight first randomly select
the geographicalareas,then randomly selectthehospitals&within the hospitalemergency units
might be randomly selected.

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e. Sequential sampling:
This sampling design is somewhat complex sample design. The ultimate size of the sample under this
technique isnotfixedinadvance,butisdeterminedaccordingto mathematical decisionrulesonthe basis
of information yieldedassurveyprogresses.Thisis usually adoptedincase of acceptance samplingplan
in contextof statistical qualitycontrol.Whenaparticular lotisto be acceptedor rejectedonthe basisof
a single sample, it is known as single sampling; when the decision is to be taken on the basis of two
samples, it is known as double sampling and in case the decision rests on the basis of more than two
samplesbutthe numberof samplesiscertainand decidedinadvance,the samplingisknownasmultiple
sampling. But when the number of samples is more than two but it is neither certain nor decided in
advance, this type of system is often referred to as sequential sampling.
Data collection
Data collectionisaprocessof systematicgatheringof datafor a particularpurpose fromvarioussources
that has been systematically observed, recorded, organized. It is the first step of statistical study. The
researchershouldkeepinmindtwotypesof dataviz.,primaryandsecondary.The primary data are those
which are collected afresh and for the first time, and thus happen to be original in character. The
secondary data, on the other hand, are those which have already been collected by someone else and
which have already been passed through the statistical process. The researcher would have to decide
whichsort of data he wouldbe using(thuscollecting) forhisstudyandaccordinglyhe will have toselect
one or the othermethodof data collection.The methodsof collectingprimaryand secondarydatadiffer
since primary data are to be originally collected, while in case of secondary data the nature of data
collectionworkismerelythatof compilation.The choice of proceduresusuallydependsonthe objectives
and design of the study and the availability of time, money and personnel.
Purpose and importance of data collection:
a. To obtain information.
b. To keep on record.
c. To make decisions about important issues.
d. To pass information onto others.
e. For research study (Data collection is an extremely important part of any research because the
conclusions of a study are based on what the data reveal).
Sources of Data:
1. Internalsourceof data:Many institutionsanddepartmentshave informationabouttheirregular
functions, for their own internal purposes which constitute the internal source of data. When
those information are used in any survey is called internal sources of data.

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Example:
a. Data gathered from the sales department to determine revenue, profit, and the bottom line.
b. Data of a social welfare society.
2. Externalsource:Wheninformationiscollectedfromoutsideagenciesiscalledexternal sourcesof
data. Such typesof data are eitherprimaryor secondary whichwe discussedabove.Thistype of
information can be collected by census or sampling method by conducting survey.
Factors to be considered before data collection:
a. Nature, scope & objective of the enquiry
b. Sources of information
c. Availability of fund
d. Techniques of data collection
e. Availability of trained persons
Primary data and its collection techniques:
Data collected by investigator from personal experimental studies for a specific research goal is called
primarydata. The data are collectedspeciallyforanexperimental researchprojects.Primarydataisused
when secondary data are unavailable and inappropriate. Data are to be unique, original, reliable and
accurate innature.Primarydata has notbeenchangedor alteredbyhuman beings,therefore itsvalidity
is greater than secondary data.
Merits and Demerits of Primary data:
Methods of Primary Data collection:
There are several methodsof collectingprimarydata,particularlyinsurveysand descriptive researches.
Important ones are:
a. Observation method
b. Interview method (direct/ indirect)
c. Questionnaires,
Merits Demerits
a. Targeted issues are addressed a. Evaluated cost
b. Data interpretation is better b. Time consuming
c. High accuracy of data c. More numberof resourcesare required
d. Addressasspecificresearchissues d. Inaccurate feedback
e. Greater control of data e. Required lot of skill with labor

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d. Schedules
e. Focus group discussion (FGD)
f. Community forums and public hearings
g. Case studies
h. Other methods which include (1) warranty cards; (2) distributor audits; (3) pantry audits; (4)
consumer panels; (5) using mechanical devices; (6) through projective techniques; (7) depth
interviews, and (8) content analysis.
Observation method:
The observation method is the most commonlyusedmethodespeciallyin studiesrelating to behavioral
sciences. Observationbecomes a scientific tool and the method of data collection for the researcher,
whenitservesaformulatedresearchpurpose,issystematicallyplannedandrecordedandissubjected to
checks and controls on validity and reliability. Under the observation method,the information is sought
by way of investigator’s own direct observation without asking from the respondent.
The mainadvantage of this methodisthatsubjective biasiseliminated,if observationisdone accurately.
Secondly, the information obtained under this method relates to what is currently happening; it is not
complicated by either the past behavior or future intentions or attitudes. Thirdly, this method is
independent of respondents’ willingness to respond and as such is relatively less demanding of active
cooperationon the part of respondentsashappensto be the case in the interview orthe questionnaire
method. This method is particularly suitable in studies which deal with subjects (i.e., respondents) who
are not capable of giving verbal reports of their feelings for one reason or the other.
However, observation method has various limitations. Firstly, it is an expensive method. Secondly, the
informationprovidedbythismethodisverylimited.Thirdly,sometimesunforeseenfactorsmay interfere
withthe observationaltask.Attimes,the factthatsome peopleare rarelyaccessible to directobservation
creates obstacle for this method to collect data effectively.
In case the observation is characterized by a careful definition of the units to be observed, the style of
recordingthe observedinformation,standardizedconditionsof observationandthe selectionof pertinent
data of observation,thenthe observationiscalledasstructuredobservation.Butwhenobservation isto
take place withoutthese characteristicsto be thoughtof inadvance,the same is termedas unstructured
observation.
If the observerobservesbymakinghimself,more or less,a memberof the grouphe is observingsothat
he can experiencewhatthe membersof the group experience,the observation iscalledasthe participant
observation. When the observer observes as a detached emissary without any attempt on his part to
experience through participation what others feel, the observation of this type is oftentermed as non-
participant observation.

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Interview Method:
The interviewmethodof collectingdatainvolvespresentationof oral-verbal stimuliandreplyin termsof
oral-verbal responses. This method can be used through personal interviewsand, if possible, through
telephone interviews.
(a) Personal interviews: Personal interview method requires a person known as the interviewer asking
questionsgenerallyinaface-to-facecontacttothe otherpersonorpersons. Thissortof interview maybe
in the form of direct personal investigation or it may be indirect oral investigation.In the case of direct
personal investigation the interviewer has to collect the information personally from the sources
concerned.He has to be on the spot and has to meetpeople fromwhomdata have to be collected. This
methodis particularlysuitable forintensive investigations.Butin certaincases it may not be possible or
worthwhile to contact directly the persons concerned or on account of the extensive scope of enquiry,
the direct personal investigation technique may not be used. In such cases an indirect oral examination
can be conductedunderwhichthe interviewerhasto cross-examine otherpersonswhoare supposedto
have knowledge about the problem under investigation and the information, obtained is recorded.
Example:
Most of the commissions and committeesappointed by government to carry on investigations make use
of this method.
Structured interviews: Interviews that involve the use of a set of predeterminedquestions and of highly
standardized techniques of recording is called structured interview.
Unstructured interviews are characterized by a flexibility of approach to questioning. Unstructured
interviewsdonotfollowasystemof pre-determined questionsandstandardizedtechniquesof recording
information. In a non-structured interview, the interviewer is allowed much greater freedom to ask, in
case of need, supplementary questions or at times he may omit certain questions if the situation so
requires. Unstructured interviews also demand deep knowledge and greater skill on the part of the
interviewer.
Example:
Unstructured interview,however,happensto bethecentral techniqueof collecting information in caseof
exploratory or formulative research studies.
Focused interview ismeant to focus attentionon the givenexperience of the respondentandits effects.
Under it the interviewer has the freedom to decide the manner and sequence in which the questions
wouldbe askedandhasalsothefreedomtoexplore reasonsandmotives.The maintaskof theinterviewer
in case of a focused interview istoconfine the respondenttoa discussionof issues withwhichhe seeks
conversance.Suchinterviewsare usedgenerallyinthe developmentof hypothesesandconstituteamajor
type of unstructured interviews.
Example:
Clinical interview is concerned with broad underlying feelings or motivations or with the course of
individual’s life experience.

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The merits of the interview method are as follows:
a. More information and that too in greater depth can be obtained.
b. Interviewer by his own skill can overcome the resistance, if any, of the respondents; the
interview method can be made to yield an almost perfect sample of the general population.
c. There is greater flexibility under this method as the opportunity to restructure questions is
always there, especially in case of unstructured interviews.
d. Observation method can as well be applied to recording verbal answers to various questions.
e. Personal information can as well be obtained easily under this method.
f. Samples can be controlled more effectively as there arises no difficulty of the missing
returns; non-response generally remains very low.
g. The interviewer can usually control which person(s) will answer the questions. This is not
possible in mailed questionnaire approach. If so desired, group discussions may also be
held.
h. The interviewermaycatchthe informantoff-guardand thus may secure the most spontaneous
reactions than would be the case if mailed questionnaire is used.
i. The language of the interview can be adopted to the ability or educational level of the
person interviewed and as such misinterpretations concerning questions can be avoided.
j. The interviewer can collect supplementary information about the respondent’s personal
Characteristics and environment which is often of great value in interpreting results.
The demerits of the interview method are as follows:
a. It is a very expensive method, especially when large and widely spread geographical sample is
taken.
b. There remains the possibility of the bias of interviewer as well as that of the respondent; there
also remains the headache of supervision and control of interviewers.
c. Certain types of respondents such as important officials or executives or people in high income
groupsmay notbe easilyapproachable underthismethodandtothatextentthe datamayprove
inadequate.
d. This method is relatively more-time-consuming, especially when the sample is large and recalls
upon the respondents are necessary.
e. The presence of the intervieweronthe spotmayover-stimulate therespondent,sometimeseven
to the extent that he may give imaginary information just to make the interview interesting.
f. Under the interview methodthe organization requiredforselecting,trainingandsupervisingthe
field-staff is more complex with formidable problems.
g. Interviewing at times may also introduce systematic errors.
h. Effective interview presupposes proper rapport with respondents that wouldfacilitate free and
frank responses.
i. This is often a very difficult requirement.

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Data collection through schedules:
This method of data collection is verymuch like the collection of data through questionnaire, with little
difference whichliesinthe factthatschedules(proformacontainingasetof questions) are beingfilled in
by the enumerators who are specially appointed for the purpose. These enumerators along with
schedules, go to respondents, put to them the questions from the proforma in the order the questions
are listed and record the repliesin the space meant for the same in the proforma.In certain situations,
schedules may be handed over to respondents and enumerators may help them in recording their
answers to various questions in the said schedules. Enumerators explain the aims and objects of the
investigation and also remove the difficulties which any respondent may feel in understanding the
implications of a particular question or the definition or concept of difficult terms.
Thismethodrequiresthe selectionof enumeratorsforfillingupschedulesorassistingrespondents tofill
up schedules and as such enumerators should be very carefully selected. The enumerators should be
trained to perform their job well and the nature and scope of the investigation should be explainedto
them thoroughly so that they may well understand the implicationsof different questions put in the
schedule.Enumeratorsshouldbe intelligentandmustpossessthe capacityof cross examination inorder
to findout the truth. This methodof data collectionisveryuseful inextensive enquiriesandcan leadto
fairlyreliableresults.Itis,however,veryexpensive andisusuallyadoptedininvestigationsconductedby
governmental agencies or by some big organizations.Population censusall over the world is conducted
through this method.
Difference between interview method and schedule method of data collection
Interviews Schedules
Questionnaire is generally sent through mail to
informants to be answered as specified
in a covering letter
Generallyfilledoutbythe researchworkeror the
enumerator, who can interpret questions when
necessary.
Questionnaire is relatively cheap and economical
since we have to spend money
Schedules is relatively more expensive since
considerable amount of money
Non-response is usually high in case of
questionnaire
Non-response cases is generallyvery low in case
of schedules
It is not always clear as to who replies In case of schedule the identity of respondent is
known.
Questionnaire method is likely to be very slow
since many respondents do not return the
questionnaire in time
Schedulesthe information iscollectedwellintime
Personal contact is generally not possible in case
of the questionnaire
In case of schedules direct personal contact is
established with respondents.
Can be used only when respondents are literate
and cooperative
In case of schedules the information can be
gathered even when the respondents happen to
be illiterate.

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Merits
Direct behavioral study
Real & personal
experience record
Make possible the
study of social change
Increase analysis
ability & skills
Demerits
One case almost
differentfromanother
case
Personal bias
Use only in limit
sphere
More time & money
consuming
Data collection through FGDs method:
FGD isuseful to furtherexplore atopic,providinga broaderunderstandingof whythe target group may
behave or think in a particular way. It assist in determining the reason for attitudes and beliefs. It is
conducted with a small sample of the target group and is used to stimulate discussion and gain greater
insights.
Merits
 Useful when exploring cultural values and health beliefs
 Can be used to explore complex issues
 Can be used to develop hypothesis for further research
 Do not require participants to be literate
Demerits
 Lack of privacy/anonymity
 Potential for the risk of ‘group think’
 Potential for group to be dominated by one or two people
 Group leader needs to be skilled at conducting focus groups, dealing withconflict, drawing out
passive participants
 Time consuming to conduct and analyze
Case study method
It isthe methodof comprehensive studyof social unitwhichmaybe a person,afamily,aninstitution,an
organization or a community
Wider and more representative distribution of
sample is possible under the questionnaire
method
There usually remains the difficulty in sending
Enumerators over a relatively wider area.
Risk of collecting incomplete and wrong
information is relatively more under the
questionnaire
The information collected is generally complete
and accurate as enumerators can remove the
difficulties

18
Information through agencies
In thismethodof data collection local agentsorcorrespondentswill be appointed& they will collectthe
informationandtransmitittothe office orperson. Theydoaccording to theirownwaysandtastes.Such
method is adopted by newspapers, agencies, etc. The informants are generally called correspondents.
Thismethodissuitable inthose caseswhere the informationistobe obtainedatregularintervalsfroma
wide area.
There are many merits of this method. Extensive informationcan be obtained. It is the most cheap and
economical method. Speedy information is possible to obtain. It is useful where information is needed
regularly. Beside there are other demerits of this method. The information may be biased. Degree of
accuracy cannot be maintained in this method. Uniformity cannot be maintained and Data may not be
original.
Collection of Secondary data:
Secondarydatameansdata thatare alreadyavailablei.e.,theyrefer tothe datawhichhave already been
collectedandanalyzedbysomeone else.Whenthe researcherutilizessecondarydata,thenhe hastolook
intovarioussources fromwhere he can obtain them.In thiscase he is certainlynot confrontedwiththe
problems that are usually associated withthe collection of original data. Secondary data may either be
published data or unpublished data. Usually published data are available in:
 Various publications of the central, state are local governments;
 Various publications of foreign governments or of international bodies and their
subsidiary organizations;
 Technical and trade journals;
 Books, magazines and newspapers;
 Reports and publications of various associations connected with business and industry,
banks, stock exchanges etc.
 Reportspreparedbyresearchscholars,universities,economists,etc. in different fields;
 Public records and statistics, historical documents, and other sources of published
information. The sources of unpublished data are many; they may be found in diaries,
letters, unpublished biographies and autobiographies and also may be available with
scholarsandresearchworkers,tradeassociations,laborbureausandotherpublic/private
individuals and organizations.
Selection of appropriate method for collection of data.
There are various methods of data collection. As such the researcher must judiciously select the
method/methods for his own study, keeping in view the following factors:

19
1. Nature, scope and objectofenquiry: Thisconstitutesthe mostimportantfactoraffectingthe choiceof
a particular method. The method selected should be such that it suits the type of enquiry that is to be
conductedbythe researcher.Thisfactorisalso importantindecidingwhetherthe dataalreadyavailable
(secondary data) are to be used or the data not yet available (primary data) are to be collected.
2. Availability of funds: Availability of funds for the research project determines to a large extent the
method to be used for the collection of data.
3. Time factor: Availability of time has also to be taken into account in deciding a particular method of
data collection.
4. Precisionrequired:Precisionrequiredisyetanotherimportantfactor to be consideredatthe time of
selecting the method of collection of data.
Types of Research design:
A research design is simply the framework or plan for a study that is used as a guide in collecting and
analyzing the data. “Research design is the plan,structure and strategy of investigation conceived so as
to obtainanswersto researchquestionsandto control variance”(Kerlinger).Itisalsocalledas the “Map
or Blue print” of the study.
As such the designincludesan outline of whatthe researcherwill dofromwritingthe hypothesisandits
operational implicationsto the final analysisof data.More explicitly,the designdecisionshappentobe in
respect of:
a. What is the study about?
b. Why is the study being made?
c. Where will the study be carried out?
d. What type of data is required?
e. Where can the required data be found?
f. What periods of time will the study include?
g. What will be the sample design?
h. What techniques of data collection will be used?
i. How will the data be analyzed?
j. In what style will the report be prepared?
Purpose of research design:
 To minimize expenditure
 To facilitate smooth scaling
 To collect relevant data and technique
 To provide blue print for plans
 To provide an overview to other experts

20
Overall research design into the following parts:
 Sampling design which deals with the method of selecting items to be observed for the given
study;
 Observational design which relates to the conditions under which the observations are to be
made.
 Statistical design which concerns with the question of how many itemsare to be observed and
how the information and data gathered are to be analyzed;
 Operational design which deals with the techniques by which the procedures specified in the
sampling, statistical and observational designs can be carried out.
Research design must contain following characteristics:
 A clear statement of the research problem;
 Procedures and techniques to be used for gathering information
 The population to be studied;
 Methods to be used in processing and analyzing data.
Before describing the different research designs, it will be appropriate to explain the various concepts
relating to designs so that these may be better and easily understood.
1. Dependent and independent variables:
A conceptwhichcantake ondifferentquantitative valuesiscalled avariable. Conceptslikeweight,height,
income are all examplesof variables.Phenomenawhichcantake on quantitativelydifferent valueseven
indecimal pointsare called‘continuousvariables’. Butall variablesare notcontinuous.If theycanonlybe
expressed in integer values, they are non-continuous variables or in statistical language ‘discrete
variables’. Age is an example of continuous variable, but the number of children is an example of non-
continuousvariable.If one variable dependsuponor isa consequence of the othervariable,itistermed
as a dependent variable, and the variable that is antecedent to the dependent variable is termed as an
independentvariable. Further,if inadditiontobeing dependentuponage,heightalsodependsupon the
individual’s sex, then height is a dependent variable and age and sex are independent variables.
2. Extraneous variable: Independentvariablesthatare not relatedto the purpose of the study,but may
affect the dependent variable are termed as extraneous variables. Intelligence may as well affect the
social studies achievement, but since it is not related to the purpose of the study undertaken by the
researcher, it will be termed as an extraneous variable.
3. Control: One importantcharacteristicof a good research designisto minimize the influence or effect
of extraneous variable(s). The technical term ‘control’ is usedwhenwe design the study minimizingthe
effects of extraneous independent variables.In experimental researches, the term ‘control’ is used to
refer to restrain experimental conditions.

21
4. Confounded relationship: When the dependent variable is not free from the influence of extraneous
variable(s),the relationshipbetweenthe dependentandindependentvariablesissaidto be confounded
by an extraneous variable(s).
5. Research hypothesis: When a prediction or a hypothesized relationship is to be tested by scientific
methods, it is termed as research hypothesis. The research hypothesis is a predictive statement that
relatesan independentvariable toa dependentvariable.Usuallyaresearchhypothesismustcontain, at
least, one independent and one dependent variable.
6. Experimental and non-experimental hypothesis-testingresearch:Whenthe purpose of researchisto
testaresearchhypothesis,itistermedashypothesis-testingresearch.Itcanbe of theexperimentaldesign
or of the non-experimentaldesign. Researchinwhichthe independentvariableismanipulatedistermed
‘experimental hypothesis-testing research’ and a research in which an independent variable is not
manipulated is called ‘non-experimental hypothesis-testing research’.
7. Experimental and control groups: In an experimental hypothesis-testing research when a group is
exposedtousual conditions,itistermeda ‘control group’,butwhenthe group isexposedto some novel
or special condition, it is termed an ‘experimental group’
8. Treatments:The differentconditionsunderwhichexperimentalandcontrol groupsare putare usually
referred to as ‘treatments’.
9. Experiment: The process of examining the truth of a statistical hypothesis, relating to some research
problem, is known as an experiment. For example, we can conduct an experiment to examine the
usefulnessof acertainnewlydevelopeddrug.Experimentscan be of twotypes’viz., absolute experiment
and comparative experiment.
10. Experimental unit(s): The pre-determinedplots or the blocks, where different treatments are used,
are known as experimental units.
Observational study:
Thisstudytype isbasedonnaturallyoccurringevents whereitobservesandmeasuresthe characteristics
of interestto the study. It doesnot intervene orcontrol the factors relatedto the exposure oroutcome
and the researcher has no control over the study.
It is further categorized into:
1) Descriptive study 2) Analytical study
Descriptive study:
It describes the population or phenomenon being studied in a completely natural, unchanged
environment. Study is designed primarily to describe “what”, “who” “where” or “when”. It involves
describing the characteristics of a particular situation, eventand case in term of time, place and person
to generate hypotheses. Alsoitdoesnotseekexplanationorcauses,nor doesittry to findwhichgroupis
betterrelative toother. Itprovidesbaseline datatolauncha Programme andcan measure achievements
made. Data’s may be either quantitative or qualitative type.

22
Example:
 Estimating prevalence of blindness in diabetic patients.
 Estimating prevalence of low vision in keratoconus.
Categories of descriptive studies:
1. Case study design:
A case studyis definedasthe use of a single personinaresearchstudy. A case studyisan in-depthstudy
of a particularresearchproblemratherthana sweepingstatistical surveyor comprehensive comparative
inquiry. It generally describes features of a new or rare disease entity. In clinical medicine the
characteristics of so far unrecognized illness may be documented as a case study. It can be called up as
firststeptowardbuilding upaclinical picture of thatillness. Itcanleadto a hypothesis. Itallowstogaina
lot of in-depth,detailedinformation due tothe close examinationof single case. Itsdisadvantage isthat
it might not be true for others populations.
2. Case series design:
A Series of case study will ultimately form case-series. Case series can be both consecutive and
nonconsecutivetype.It leadstothe generationof hypotheses.Itiseasytowrite.The observationscanbe
extremely useful to other investigators. But case series are especiallyvulnerable to selection bias; they
are not able for conclusive decisions. There is lack of control group.
Example:
Studiesthatreporton a seriesof patientswithacertainillnessand/orasuspectedlinkedexposure draw
their patients from a particular population (such as a hospital or clinic) which may not appropriately
represent the wider population.
Internal validityof case seriesstudiesisusuallyverylow,due tothe lackof a comparator groupexposed
to the same array of interveningvariables.Forexample,the effectsseenmaybe whollyor partlydue to
interveningeffectssuchas the placeboeffect,Hawthorne effect,Rosenthal effect,time effects,practice
effectsor the natural historyeffect.Calculatingthe difference ineffectsbetweentwotreatmentgroups
Descriptive
studies
Individual
Case study
Case series
Crosssectional
descriptive
Aggregate
Ecological
studies

23
assumed to be exposed to a very similar array of such intervening effects allows the effects of these
interveningvariablestocancel out.Henceonlythe presenceof acomparatorgroup,whichisnotafeature
of case-series studies, will allow a valid estimate of the true treatment effect.
Example:
 Realistic approach for rare disorders
 Access prevalence of disease.
3. Cross sectional descriptive design:
The main purpose of this study design to learn about the characteristics of a population at one point in
time (snap shot). Design includes no comparison or control group to make a comparison against.
Population includes all members of a small, defined group or a sample from a large group. It produces
estimates of the prevalence of the population characteristic of interest (eg. a disease). Cross-sectional
designs are used for population-based surveys and to assess the prevalence of diseases in clinic-based
samples. These studies can usually be conducted relatively faster and are inexpensive. They may be
conducted either before planning a cohort study or a baseline in a cohort study. These types of designs
will give us informationabout the prevalence of outcomes or exposures; this information will be useful
for designingthe cohortstudy.However,since thisisa1-time measurementof exposureandoutcome,it
isdifficulttoderive causal relationshipsfromcross-sectional analysis.We canestimate the prevalence of
disease incross-sectional studies.Furthermore,we will alsobe able to estimate the oddsratiosto study
the association between exposure and the outcomes in this design.
Example:
 To estimate prevalence of a health condition or prevalence of behavior, risk factor or potential
for disease. E.g: studying smoking leading to lung cancer in COPD.
 To learn about characteristics such as knowledge, practice and attitudes of individuals in a
population. E.g: use of seat belts in preventing injuries in accidents.
 To monitor trends over time with serial cross sectional studies.

24
Analytical study
Cohort study
Case control
study
Cross sectional
analytical study
4. Ecological study design.
An ecological study is an observational study definedby the level at which data are analysed, namely at
the population or group level,rather than individual level.Ecological studies are oftenused to measure
prevalence andincidence of disease,particularlywhen disease israre.They are inexpensive andeasy to
carry out,usingroutinelycollecteddata,but theyare prone to bias and confounding.Also,because they
are area-level studies,care must be taken when extrapolating either to individuals within the area level
of measurement, orto a higherpopulationlevel.Although otherstudydesignsare generallyconsidered
more reliable, particularly in the inference of causation, the population context of individual
characteristicshasbeenshowntobe a strongerdeterminantof diseaseatpopulation levelthanindividual
level risk factors.
Example:
1) Annual death rate due to diabetes among youth <20 years of age.
Analytical study
a) Cohort study:
A “Cohort” is a group of people who share a common attribute or experience.
Example: Individuals born in the same year or live in same geographical location or exposed to same
radiation, etc.
Itshowsdirectcause-effectrelationshipbetweenindependentanddependentvariable.Cohortstudyalso
known as longitudinal or follow-up studies. Cohort studies primarily show causation while case control
show association. Subjects are sampled based on the presence (Exposed) or absence (Unexposed) of a
risk factor of interest and followed up over time to ascertain outcome.
Exposed: Particular risk factor responsible for the development of disease or particular program
responsible for changing the outcome of interest.
Unexposed: Not exposed to particular risk factor or the Program (will act as control).

25
The above diagram illustrates how cohort study is set out. We start by identifying study population i.e.
cohort and then determiningwhoisexposedandwhoisnot. Thencohort isfollowedforwardintime for
a periodwhichisgenerallyinyears,toallow exposure toresultindiseasedstate anddetermine ultimate
state of bothexposedandunexposedgroups.Itisverycritical thatcohort membersnothave the disease
at the beginning of study. Cohort study design can be used to find multiple outcomes from single
exposure. Itisappropriate forrare exposuresordefinedcohortalsoitensurestemporalitysinceexposure
occurs before observed outcome.
Cohort can further be divided into Prospective cohort and Retrospective cohort.
Prospective study:It isthe hallmarkof cohortstudy.Itgoesforwardintime fromthe time of exposure to
the point of follow up to determine if the disease has occurred.
Retrospective study: It goes backwards in time to determine whether exposure has occurred in
population inwhichtheoutcomeof interestisalreadypresent. Thistype of studyis alsocalledas historical
study. It is easier to conduct and less expensive.
Advantages and disadvantages of cohort study:
Advantages Disadvantages
 Establish population based incidence  Lengthy
 Temporal relationship inferred.  Costly
 Time-to-event analysis possible  Not suitable for rare/long latency diseases.
 Used when randomization not possible  Require very large samples
 Reduces selection and information bias  Non response, loss to follow up
Study
population
Exposed
Disease
Non
disease
Non
Exposed
Disease
Non
disease
Present Future
Direction
of inquiry

26
b) Case control study:
It is also known as association study not causation study. It simply state that there is some type of
associationbetweenindependentanddependentvariable. Itcanassignnumericvalue tothatassociation
using“odds ratio”. It do not state that the independentvariablehascausedthe dependentvariable.Itis
generally used for rare conditions such as infectious conditions. Subjects are based on the presence
(Cases) orabsence (Controls) of the diseaseof interest.Informationiscollectedaboutearlierexposure to
risk factors of interest so case control study is always a Retrospective Study.
 Cases: Diseased Persons or Condition of Interest
 Control: Non Cases or Not Diseased Persons or Without the Condition of Interest
Example: lung cancer patients can be chosen as cases and normal patients or other patients having any
other disease than lung cancer can be chosen as controls to see the effect of smoking.
Given above diagram depicts how a case control study is designed. We start by identifyingcases from a
population to be studied, then we select appropriate controls from the same population. Then,
informationiscollectedonexposure historytothe independentvariable forbothcasesandcontrols,then
compare exposure between cases and control to see if there is a difference.
Exposed
None exposed
Cases
Controls
Population
Exposed
None exposed
PresentPast
Direction
of inquiry

27
Advantages and Disadvantages of Case control study
 High information yield with few
participants.
 Selectionofappropriate controlgroupcan
be difficult.
 Can study long term effects on short
period of time.
 Cannotestimate incidence or prevalence
 Useful for rare outcomes.  Limited outcomes can be studied
 Highly susceptible to recall biases
c) Cross sectional analytical study:
It will take asnapshotof a population.Inthisstudymethodpeople are studiedata pointintime without
any follow-up. It can measure attitudes, beliefs,behaviors,personal or family history, genetic factors,
existingorpasthealthconditions,oranythingelse thatdoesnotrequire follow-uptoassess. Itexamines
the relationshipbetweenadisease andanexposure amongindividualsinadefinedpopulationata point
in time. In this method of study both antecedent and outcome are observed at the same time. This
method is appropriate to generate hypothesis regarding etiology.
Advantage and disadvantage of cross sectional analytical study
Comparison between Cohort, Case control and Cross sectional analytical study
Basis Cohort study Case control study Cross sectional
analytical
Main antecedent Known Elicited Elicited
Outcome Elicited Known Elicited
Recruitment of subject Basis of antecedent Basis of outcome Neither outcome nor
antecedent
Definition of case Subject with
specifiedantecedent
Subject with specified
outcome
Any subject in defined
population
Evaluation & control of
confounders
Poor Good Fair
No of subjects Large Small Large
Measure of disease
frequency
Incidence Odds obtained from
antecedent
Prevalence
Advantage Disadvantage
 Fast and inexpensive  Can’t determine causal relationship
 No loss to follow-up  Doesn’t tell the flow of events
 Can target a larger sample size  Impractical for rare diseases
 Risk for non-response

28
If all factors are not
known
Best Not appropriate Less appropriate
Time and money Most expensive Least expensive In between
Experimental Research design:
It require deliberate human intervention to change the course of events. Independent variables are
changedon purpose bythe experimentertoobserve the response of dependentvariable tothatchange.
This is often infeasible because of difficulties enrolling participants, high costs, and big ethical issuesto
prove hypotheses.
It usually compare two groups;
 One group in which intervention takes place i.e Experimental group.
 Another group that remains untouched i.e Controlled group.
1. Clinical trial study:
Clinical trial study is a planned experiment designed to access the efficacy of
prophylactic/diagnostic/therapeutic agents, devices, regimens, procedures, etc applied to human
subjects. This is considered a Gold standard for scientific experiments.
It can be of two types:
 Animal studies
 Laboratory studies
Commonest objective of clinical trial study:
Clinical trialsare normallyconductedtoevaluatenew formsof therapy or prevention methods such as:
 New drugs/treatment
 New medical/health care technology
 New organization/delivery system of health care
 New methods of primary prevention
 New programs of screening or early detection
Clinical trial may be therapeutic or preventive.
In therapeutic clinical trial sample is selected from a large population suffering from disease and in
randomizedmanner,somewillreceivenew treatmentandotherswill receiveoldstandardtreatment.All
these individuals are followed up prospectively for a defined duration with a defined frequency. Then,
assessed again to figure out how many are cured and how many continue to have the disease.

29
In Preventive clinical trialssample istakenfromaPopulation whichissusceptibleorat riskof developing
a disease.Inrandomizedmanner,some will receivepreventionandotherswill receive placebo.Theyare
followedperiodicallyupforacertaintime andhow manyineithergroupsactuallyacquire the disease. So
that effectiveness of prevention can be determined.
Advantage and Disadvantages of Clinical trial study:
 Give a strong causality evidence  Complex, Expensive
 Control selection and confounding bias  Lack of representativeness
 Historic controls can be used in
preliminary study
 Ethical issues
 Long time required
 Participant compliance
Controlled and Non-controlled trials:
Controlledtrialsare studiesinwhichthe experimentaldrugorprocedure iscomparedwithanotherdrug
or procedure as usually previously accepted or placebo treatment. Non-controlled trials are studies in
which the experimental drug or procedure described is not being compared with another treatment.
True experimental design:
Research design where researchers have complete control over the extraneous variables & can predict
confidentlythat the observed effect on the dependable variable is only due to the manipulation of the
independent variable
It essentially consist of the following three characteristics:
 Manipulation: conscious control of independent variable by researcher to observe its effect on
dependent variable.
 Control: controlling the effects of extraneous variables on the dependent variable in which
researcher is interested.
 Randomization: meansthat every subject has an equal chance of being assigned to experiment
on random basis.
2. Randomized Controlled Trials:
RCT provides the strongest evidence for concluding causation. It provides the best insurance that the
result was due to the intervention only. Provide that each individual has the same chance of receiving
each of the possible interventions, so allocation of subjects in experimental or control group is given by
chance. AlsoRCTensuresthatknownandunknownconfoundingfactorsare equal inbothgroup, inorder
to reduce bias.

30
3. Non Randomized Controlled Trials:
It isa Clinical trial orcomparativestudieswithnomentionof randomizationaswell.Itisconsideredmuch
weaker because they do nothing to prevent bias in patient assignment.
Quasi Experimental design:
Thisinvolvesthe manipulationof independent variable toobserve toeffectondependentvariable,butit
lacks at least one of the two characteristics of the true experimental design; randomization or a control
group. It is used to establish causal relationship where researchers are unable to randomly assign the
subjectsornocontrol groupisavailable. Nonrandomizedcontrolledtrialsare quasiexperimentaldesigns.
4. Pre Experimental Design:
It is considered very weak, because the researcher has very little control over the experiment.
Single experimental groupisexposedtoa treatment, withnocontrol group, and no random assignment
of subjects. It can suitable for beginners in the field of experimental research.
5. Field trials:
In contrastto clinical trials, itinvolvespeoplewhoare diseasefree butpresumedtobe atrisk.Inthe field
trials Data collection take place in the field usually among non-institutionalized people in the general
population.Mainpurpose istopreventthe occurrence of the diseasesthatmayoccur withrelativelylow
frequency. Field trials are often huge undertakings involving major logistic and financial considerations.
Fieldtrial methodcanbe usedto evaluate interventionsaimedatreducingexposurewithoutnecessarily
measuringthe occurrence of the healtheffects. E.gBloodleadlevelsinchildrenhasshownthe protection
provided by elimination of lead paint in home environment
6. Community trials:
Inthisformof experimentthe treatmentgroupsare communitiesratherthanindividuals. Appropriatefor
diseases that have their origins in social conditions, which in turn can most easily be influenced by
intervention directed at group behavior as well as at individuals.

31
References:
 Fundamentals of research methodology and statistics by Yogesh Kumar singh.
 Research methodology: Methods and Techniques by C.R. Kothari
 Introductory biostatistics for health sciences by Michael Chernick
 Research design by John W. Creswell

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