1. by Chanchal Pramanick

2.  WhatisPopulation ?
Population is the whole area on which research is done.
 WhatisSample ?
Sample is those unit which is selected by researcher from among the
population.
 WhatisSampling?
Sampling is the process to selecting sample on the whole population

3. SAMPLE
 A population can be defined as including all people or items with the
characteristic one wishes to understand.
 Because there is very rarely enough time or money to gather
information from everyone or everything in a population, the goal
becomes finding a representative sample (or subset) of that population.
SAMPLE
TARGET POPULATION
SAMPLE UNIT

4. SAMPLING
Target Population or Universe :
The population to which the investigator wants to generalize his results.
Sampling Unit :
smallest unit from which sample can be selected
Sampling frame :
The sampling frame is the list from which the potential respondents are drawn
Telephone directory
List of five star Hotel
List of student
Sampling scheme :
Method of selecting sampling units from sampling frame
Sample: all selected respondent are sample

5. TYPES OF SAMPLING
SAMPLING
Probability Non-Probability
1. Simple Random Sampling.
2. Double Random Sampling.
3. Systematic Sampling.
4. Stratified Random Sampling.
5. Cluster Sampling.
6. Multi-Stage Sampling.
1. Judgmental Sampling.
2. Convenient Sampling.
3. Quota Sampling.
4. Snowball Sampling.

6. PROBABILITY SAMPLING

7. Characteristics
According to Good (1966), probability sample have the following
characteristics
• Each unit in the sample has some known probability of entering the
sample.
• Weights appropriate to the probabilities are used in the analysis of the
sample.
• The process of sampling is automatic in one or more steps of selection
of units in the sample.

8. Advantages
• It helps the researcher to know the size of the sample needed to
achieve any desired level if accuracy.
• The researchers also may be able to specify the chance of each unit
being selected.
• This method also helps to estimate the magnitude of error due to
sampling.

9. Disadvantages
• It depends upon how good a sampling frame is made, although this
remains a limitation in complete enumeration studies.
• In this process, only a portion of the sampling frame is examined and
so specific information on every sampling unit (people, account,
inventory, etc) are ignored.
• In small areas or rare sub-population, sampling error may be high.
• Representative of the frame may be questionable and controversial.

10. 1.Simple RandomSampling
A simple random sample is one in which each element of the population
has an equal and independent chance of being included in the sample i.e.
a sample selected by randomization method is known as simple-random
sample and this technique is simple random-sampling.
Use only ‘Homogeneous’ group of population.
Randomization is a method and is done by using a number of techniques
as :
(a) Tossing a coin.
(b) Throwing a dice.
(c) Lottery method.
(d) Blind folded method.

11. 2.DoubleRandomSampling
Use only ‘Homogenous’ group of population.

12. 3.Systematic Sampling
 Systematic sampling is an improvement over the simple random sampling. This method
requires the complete information about the population. There should be a list of
information’s of all the individuals of the population in any systematic way. Now we decide
the size of the sample.
Let sample size = n and Population size = N
 Now we select each N/nth individual from the list and thus we have the desired size of
sample which is known as systematic sample. Thus for this technique of sampling
population should be arranged in any systematic way.

13. 4.StratifiedSampling
 It is conducted when population is ‘Heterogeneous’.
 Researcher divides the whole population into Strata.
 ‘Strata’ means layer.
 Then he selects the sample according to the proportion of the population from
the each strata.
Example- Attitude of U.G Students Towards Online Learning.
1000
Girl
600
Boys
400
2 : 3
10 % 100
40
60

14. 5.ClusterSampling
 Also known as ‘Area sampling’.
 Bengali meaning of Cluster is ‘গুচ্ছ’.
 Researcher divides the whole population into various zones and then he selects one
zone randomly from their.
 All the elements of the selected zone is considered as sample.
 Not a single element of the selected zone can be throw away.
Use ‘Heterogeneous’ group of population.
Example- Effect on dengue on West Bengal.
E N
S W w

15. 6.Multi- StageSampling
Use ‘Heterogeneous’ group of population.
Example- Effect on dengue on West Bengal.
E N
S W w
Randomly selected 1,00,000
5,00,000
10,00,000
15,00,000
10%
10%
10%
10%

16. NON-PROBABILITY SAMPLING

17. Advantages
 They are quicker, cost effective and more convenient than
probability samples.
 Non-probability samples do not require a sampling frame.
 The sample size and quota requirements are usually achieved.

18. Disadvantages
 Less confidence is placed in the data obtained from samples and thus, results
obtained cannot be generalized of the entire population.
 Sampling based on convenience affects the variance within groups as well as
between groups.
 Sampling errors of these sampled cannot be determined.
 They depend exclusively on uncontrolled factors and researcher’s insight and
there is no statistical method to determine the margin of sampling errors.
 Sometimes, such samples are based on absolute frame, which does mot
adequately cover the population.
 There is considerable scope of bias in the selection of units to be included in
the sample.

19. 1.JudgmentalSampling
 Judgmental sampling also known as ‘Purposive Sampling’.
This involves the selection of a group from the population on the basis of
available information thought. It is to be representative of the total population. Or
the selection of a group by intuition on the basis of criterion deemed to be self-
evident. Generally investigator should take the judgment sample so this sampling
is highly risky.
Apply only small size Population.
Example- Effect of parents educational qualification on their child's achievement.

20. 2.Convenience Sampling
Convenience Sampling also known as ‘Accidental’ or ‘Incidental’ sampling.
In convenience sampling, the researcher select those units from the population
which are accessible to the researcher.
Subjects are chosen simply because they are easy to recruit.
This technique is considered easiest, cheapest and least time consuming.

21. Consecutive Sampling
 A type of convenience sampling.
The researcher picks a sample and conduct research over a period of time,
collect results, and then moves on to another sample.
This sampling technique gives the researcher a chance to work with multiple
samples to fine tune his/her research work to collect vital research insights.
Small population size.

22. 3.QuotaSampling
In quota sampling the researcher ensures equal or proportionate representation
of subjects depending on which trait is considered as basis of the quota.
The bases of the quota are usually age, gender, education, race, religion and
socioeconomic status.
For example, if basis of the quota is socioeconomic status and the researcher
needs equal representation of each quota, (sample size 150),
Upper Class- (Elite) 30
Upper Middle Class 30
Lower Middle Class 30 150
Working Class 30
Poor 30

23. 4.SnowballSampling
 Snowball sampling or chain-referral sampling is defined as a non-probability
sampling technique in which the samples have traits that are rare to find. This is a
sampling technique, in which existing subjects provide referrals to recruit samples
required for a research study.
 Snowball sampling method is purely based on referrals
 This sampling technique can be extensively used for conducting qualitative
research.