NON PROBABILITY SAMPLING IS A TECHNIQUE WHER IN THE SAMPLES ARE GATHERED IN A PROCESS THAT DOES NOT GIVE ALL THE INDIVIDUALS IN THE POPULATION EQUAL CHANCES OF BEING SELECTED IN THE SAMPLE

1. NONPROBABILITY
SAMPLING
Dr. Rangappa Ashi
Associate Professor
SDM Institute of Nursing Sciences
Shri Dharmasthala Manjunatheshwara
University
Dharwad. Karnataka.

3. I N T R O D U C T I O N
SAMPLING IS QUITE AN OLD IDEA PEOPLE HAVE
EXAMINEDA HAND FULOFGRAINSTO
ASCERTAINTHEQUALITYOFTHE ENTIRE LOT .
 ATEACHER MAYQUESTIONTWOSTUDENTS INA
CLASSTO CHECK IF STUDENTS HAVE
UNDERSTOOD HERCLASS.
 SAMPLING ISTHE USEOFASUBSET OF THE
POPULATIONTO REPRESENTTHEWHOLE
POPULATION.

5. T E R M I N O L O G Y
 ELEMENT: AN ELEMENT MAY BE A
PERSON,A FAMILY, A COMMUNITY, A
MEDICAL RECORD,A LABORATORY
SPECIMEN.EX; A NURSE, A BOY,A
PLANT,IN NURSING RESEARCH ,
ELEMENTS ARE HUMANS.
 POPULATION: AN ENTIRE SET OF
ELEMENTS THAT MEET SPECIFIED
CRITERIA.
 EX; AN AGGREGATE OF TREES,NURSES, BOYS
ETC.

6.  SAMPLE: A SAMPLE IS A SUBSET OF THE
POULATION ELEMENT.
EX; TASTING ONE GRAPE FROM THE WHOLE
BUNCH OF GRAPES TO PURCHASE.
 SAMPLING PLAN: IS A PROCESS THAT
INVOLVES MAKING CHOICES ABOUT WHO ,
OR WHAT TO INCLUDE IN THE SAMPLE, HOW
TO SELECT THE SAMPLE, AND HOW MANY
SUBJECTS TO INCLUDE IN THE SAMPLE FOR
A PARTICULAR STUDY.

7.  T Y P E S O F S A M P L I N G
M E T H O D S
PROBABILITY
SAMPLING
NON
PROBABILITY
SAMPLING

8. D E F I N I T I O N
 ‘‘NON PROBABILITY SAMPLING IS A
TECHNIQUE WHER IN THE SAMPLES
ARE GATHERED IN A PROCESS THAT
DOES NOT GIVE ALL THE INDIVIDUALS
IN THE POPULATION EQUAL CHANCES
OF BEING SELECTED IN THE SAMPLE’’.

9. USES OF NON PROBABILITY
SAMPLING
DEMONSTRATE THAT A PARTICULAR
 1. TO
TRAIT EXISTS IN THE POPULATION.
A RESEARCHER WANTS TO
 2. USED WHEN
DO A QUALITATIVE, PILOT, OR
EXPLORATORY STUDY.
THE POPULATION IS LIMITLESS.
 3. WHEN
 4. LIMITED TIME BUDGET AND WORKFORCE.
 5. USED IN A PILOT STUDY.
DOES NOT WANT TO
 6.WHEN RESEARCHER
GENERATE RESULTS.

10. FEATURES OF NON PROBABILTY
SAMPLING
 NO EQUAL CHANCE FOR ALL THE
INDIVIDUALS TO BE SELECTED.
 IS NOT A PRODUCT OF
RANDOMISED SELECTION.
 SELECTED ON THE BASIS OF
ACCESSIBILTY, PURPOSIVE
PERSONAL JUDGEMENT OF THE
RESEARCHER.

11. NON PROBABILITY SAMPLING
1. Purposive sampling
2. Convenience sampling
3. Snow ball sampling/ network sampling
4. Quota sampling
5. Consecutive sampling

12. TYPES OF NON PROBABILITY
SAMPLING
Purposive
sampling
Convenience
sampling
Snow ball
sampling/
Quota
sampling
Consecutive
sampling

13. Uses of non probability sampling
Particular trait
exists in the
population
In qualitative,
pilot, or
exploratory
study
Used when
randomization
is not possible
limited time
budget and
work force
When not
required to
generalize
results

14. Purposive sampling
 It is also called judgemental sampling or
authoritative sampling.
 The subjects are chosen to be a part of the sample
with specific purpose in mind.
 Samples are chosen by choice and not by chance,
through a judgement made by the researcher.
 Experts who have in depth knowledge about the
accessible population.

15.  Ex:A researcher wants to study the lived
experiences of post disaster depression among
people living in earth quake affected areas
Gujarat. In this case a purposive sampling
technique is used to select the subjects who were
the victims of the earthquake disaster and have
suffered post disaster depression living in
earthquake affected areas ofGujarat.

16. Post disaster

17. USES OF PURPOSIVE SAMPLING
when a limited number of individuals
possess the trait of interest.
viable sampling technique in obtaining
information from a very specific group of
people.

18. MERITS
 Simple to draw sample and useful in
explorative studies.
 Saves recourses requires less field work

19. DEMERITS OF PURPOSIVE SAMPLING
Requires
considerable
knowledge
Conscious bias
Reliability of
the expert cant
be evaluated
Sampling
process is
biased

20. CONVENIENCE SAMPLING
 Convenience sampling is also called accidental
sampling.
 The subjects are selected just because they are
easiest to recruit for the study
 EX: If a researcher wants to conduct a study on the
older people residing in Ludiana and the researcher
observes that he can meet several older people
coming for morning walk in a park located near his
residence .

22. Uses of convenienant
sampling
Allows the
researcher to obtain
basis data and
trends
Useful in documenting
a particular quality of a
substance

23. MERITS
less time
consuming
Easiest
cheapest

24. DEMERITS
SAMPLING BIAS
FINDINGS
CANNOT BE
GENERALISED
NOTTHE
REPRESENTATIVE
OFTHE ENTIRE
POPULATION.

25. Snow ball sampling/ network
sampling
 In snow ball sampling approach early
sample members are asked to identify
and refer other people who meet the
criteria.
 Examples: criminals, child abusers and
alcoholics.

26. SNOW BALL SAMPLING

27. TYPES OF SNOW BALL SAMPLING
 Linear snowball sampling
Exponential non discriminative snow ball
sampling
Exponential discriminative snow ball
sampling

28. MERITS
 cheap.
 Simple and cost effective.
 Needs lesser planning and lesser work force.

29. DEMERITS
 Researcher has little control over the
sampling method.
 Representativeness of the sample is not
guaranteed.
 The researcher has no idea of the true
distribution of the population and of the
sample

30. Quota sampling
Quota sampling is a combination of stratified sampling
and convenient sampling.
 In quota sampling, the population is first
segmented into mutually exclusive sub-groups, just
as in stratified sampling.Then judgement is used to
select the subjects or units from each segment
based on a specified proportion. For example, an
interviewer may be told to sample 200 females and
300 males between the age of 45 and 60.


31.  It is this second step which makes the
technique one of non-probability
sampling. In quota sampling the selection
of the sample is non-random. For example
interviewers might be tempted to
interview those who look most helpful.

32. Advantages:
 Less costly
 Administered easily
 Suitable in situation where field work done quickly
in order to reduce memory error.
 It is independent of the existence of sampling
frames.

33. DEMERITS
 Not possible to estimate the sampling errors.
 Selection Bias is more
 Respondents will be selected as per the
researcher.

34. Consecutive sampling:
 Consecutive sampling is also
called total enumerative
sampling.
 The investigator picks all the
inclusion and the exclusion
criteria.

35. Ex:If a researcher wants to study the activities of post
kidney transplant patients ,he selects all the post
kidney transplant patients who meet the designed
inclusion and exclusion criteria who are admitted
in the post renal ward in the specified time period.

36. Merits:
 Very little part on the researcher when
performing this sampling technique
 It is not expensive, not time consuming, and
not work force intensive.
 Ensures more representativeness of the
selected sample.

37. Demerits:
 The researcher has no set plans about the
sample size and sampling schedule.
 It always does not guarantee the selection of
representative sample.
 Results from the sampling technique cannot
be used to create conclusions and
interpretations pertaining to the entire
population.

38. RECAPUTALISATION
SESSION

39. CONCLUSION
 STUDIES INTENDEDTO BE PROBABILITYSTUDIES
SOMETIMES ENDUP BEING NON-PROBABILITY
STUDIES DUETOUNINTENTIONALOR
UNAVOIDABLECHARACTERISTICSOFTHE
SAMPLING METHOD.
 INCOMPARISON PROBABAILTY SAMPLING IS
BETTERTHAN NON PROBABILITYSAMPLING
BECAUSE IT REDUCESTHE ERROROFCONSCIOUS
BIAS,AL
THOUGHTIMECONSUMING .

40. ASSIGNMENT
 Find the difference between probability and non
probability sampling?

41. REFERENCES
SURESH . K.SHARMA
POLITAND BECK
BASAVANTHAPPA
SHARON MANON

42. T H A N K
Y O U