3. • The individual units from the population are
selected at random.
• Chance of each item of the population being
included in the sample is equal.
• Also known as representative sampling.
• Can be done by lottery and table of random
numbers.
• In lottery, all items of the universe are give
different numbers and mixed up in a container
so as to pick the numbers randomly.
• In table method, all items are given in a table
and selected randomly.
4. Merits :
• No possibility of being personally bias
• With the increase size of the population, it becomes representative of
the whole population.
• Accuracy of the sample can be tested with other sample.
Demerits :
• Unsuitable where some items of the universe are necessary to be
selected
• Not suitable where area of inquiry is limited.
• Not suitable where units of the universe are heterogeneous.
5. Stratified Sampling/ Mixed Sampling
The universe is divide into various groups.
Each group of the population is called a stratum.
Then, a sample is drawn from each stratum at
random.
These samples are then combined to form a single
sample of the universe.
For ex :
In a village of 3000 population, we want to make an
economic survey. If 1000 people are of above a8
years of age, they will constitute the universe.
Farmers Traders servicemen Artisans Casual
workers
total
400 50 100 300 150 1000
6. Merits :
• A true representative of the universe as selected from each strata.
• Ensures greater accuracy due to presence of homogeneous items.
• Useful to study the characteristics of different parts of the population.
• Useful where extreme values in the population as they can be grouped
into strata.
Demerits :
• Results will not be reliable if universe is not divided properly.
• A complex method and requires experts or trained personnel.
7. Systematic Sampling
• All units of the universe are arranged in a systematic manner on
numerical, geographical, alphabetical or some other basis.
• Each 2nd, 3rd or any number on random basis from the list of the
universe is selected.
• Example :
• We have to take the sample of 10 students from 100 students. First,
we will select a number and suppose this no is 4. then we will include
every 10th student beginning from 4 in sample.
• In this way 4,14,24,34,44,54,64,74,84,94 will be included in the
sample.
8.
9. Merits :
• Convenient to adopt.
• Economical in case of time and money.
• Results are satisfactory.
Demerits :
• Are not generally random samples.
• If the population is arranged in a wrong manner, results will be
misleading.
• Feasible only when units are arranged systematically.
10. Multi-stage Sampling
• Sample is taken out in different stages.
• First – various homogeneous groups are selected from the population.
• Second – elementary sampling units are selected from each of these groups.
• Further stages may be added as per need.
• Example :
• We have to select a sample of 1000 households from Uttar Pradesh. For this we
will divide state in to districts and few districts are selected. Then districts are
sub-divided into tahsils , and some tahsils are selected.
• Tahsils are subdivided into villages and some villages are selected.
• Then villages are divided into households and some households are selected at
random.
• In this way the size of the sample goes on decreasing.
11.
12. Deliberate Sampling/ Purposive Sampling/
Judgement Sampling
• The sample is taken out of the
universe according to desire or need
of the investigator.
• Example :
• If a sample of 10 students is to be
taken from a population of 100
students to analyze their habits, the
investigator would select only those
students whom he considers true
representatives of the population.
13. Merits :
• Very simple
• Most suitable where some items are important to be included.
• Economical also
• Significant where all units of the universe are homogeneous.
• Conclusions will be sufficiently reliable.
Demerits :
• Not scientific, as results are to be affected by personal biasness.
• The selection of the sample would differ from person to person.
• Lacks accuracy
14. Quota Sampling
• The whole universe is divided into various groups on the basis of
different characteristics such as sex, occupation, age, income, etc.
• Quota of persons is fixed for each group for each investigator.
• Example :
• In a budget reaction survey, the interviewers are told to interview 100
people living in a particular area. But they have to interview 25%
housewives, 25% fixed income group people, 20% producers, 15%
farmers, 10% traders and the remaining 5% students.
15.
16. Merits :
• Very useful for public opinion surveys.
• Results can be satisfactory in case interviewers are trained.
• Requires less time and money as compared to other sampling
methods.
Demerits :
• Biased
• Not very popular
• Persons may refuse to respond
