Research sampling techniques. sampling used in thesis.

1. RESEARCH AND SAMPLING TECHNIQUES
IN QUANTITATIVE RESEARCH

2. CLINICAL RESEARCH
• Clinical research is a structured process of investigating facts and theories and of
exploring connections, with the purpose of improving individual and public
health. It proceeds in a systematic way to examine clinical or social conditions
and outcomes, and to generate evidence for decision-making

4. POPULATION
 Group of people or subjects according to the scope of the study
 Population is a group of interest to the researcher to whom he
would like to generalize the results of his study.
 They always share a common set of characteristics

5. • Target population
• Population to which the researcher would ideally like to generalize his study
results.
• It is rarely available.
• Accessible population
• Population from which the researcher can realistically select subjects, also
known as available population.

6. SAMPLE
 The subset of population
 Should be true representative of population

7. SAMPLING TECHNIQUE
 The procedure of selecting certain number of study units from
a defined population is called Sampling.
 A representative sample has all important characteristics of the
population from which it is drawn.

8. WHY SAMPLING???
 To get information about a population from a sample
 The results provided from the studies on the samples can give us
estimate of the values of the population.
 We, with the help of proper sampling techniques can provide accurate
and reliable estimates of the population characteristics

9. ADVANTAGES OF SAMPLING
1. Sampling Saves Money And Time
2. Useful when sampling unit are sensitive
3. For Infinite Population
4. Smaller Non-Response

10. STAGES IN SELECTING A SAMPLE
1. Define the target population
2. Select accessible population
3. Determine sampling method
4. Plan process for selecting sampling units
5. Determine sample size
6. Select actual sampling units

11. TYPES OF SAMPLING
1. Probability Sampling
2. Non-probability sampling

12. Snow Ball Sampling
Convenience Sampling
Purposive Sampling
Or
Judgemental Sampling
Sampling Techniques
Probability Sampling
Non Probability Sampling
Quota Sampling Simple Random
Sampling
Systematic Sampling
Stratified Sampling
Cluster Sampling

13. PROBABILITY SAMPLING
 Probability – Sample is selected based on a random process (which
means it is based on chance).

14. NON-PROBABILITY SAMPLING
 Non-probability– Sample is selected using some non random
process (not based on chance).

15. TYPES OF PROBABILITY SAMPLES
1. Simple Random Sample
2. Systematic Sample
3. Stratified Random Sample
4. Cluster Sample

16. SIMPLE RANDOM SAMPLING
• Each element in the population has an equal probability
(chance) of being selected for the sample

17. STRATIFIED RANDOM SAMPLING
 Strata – is a group of people who share a common
characteristics
 Examples of strata– race, gender, marital status.

18. PROCEDURE
1. Strata
2. No Overlapping
3. Homogenous Groups
4. Random Sample taken from Each Stratum
5. Parameter Estimates

19. CLUSTER SAMPLING
 The population is first divided into separate groups of elements
called clusters.
 Ideally, each cluster is a representative small-scale version of the
population (i.e. heterogeneous group).
 A simple random sample of the clusters is then taken.
 All elements within each sampled (chosen) cluster form the sample.

20. SYSTEMATIC SAMPLING
 Nth subject
 It has all properties of S.R.S.

21. NON PROBABILITY SAMPLING
 Obtain subjects in some nonrandom way.
 Typically volunteers

22. CONVENIENCE SAMPLING
 Samples are selected on the basis of availability and easy access by
the researcher.
 Individuals/ elements were included only because they were
available and convenient to recruit
 Haphazard
 May not be representative

23. QUOTA SAMPLING
 Divide the population into various categories
 Determine the number of people to be selected for each
category

24. PURPOSIVE OR JUDGMENTAL SAMPLE
 Select your sample on the basis of your knowledge of the
population and nature of your research aims.

25. SNOWBALL SAMPLE
 Find someone who fits the criteria for the study accidental
/convenience sample)
 Interview person and at end of interview, you ask if he/she knows of
other people who meet the study criteria and may be willing to
participate

26. USES OF NON PROBABILITY
SAMPLING
1. This type of sampling technique is used when the researcher
wants to show that a certain trait exists in the entire population.
2. When randomization is not possible e.g. in cases of almost
limitless populations.
3. When the researcher is conducting a pilot, exploratory or a
qualitative study.
4. When the researcher has limitations of budget, time, resources,
manpower etc.
5. When the researcher is not aiming to generalize results on the
entire population

27. DISADVANTAGES OF NON PROBABILITY
SAMPLING
1. The sample produced may or may not be an accurate
representation of the entire population.
2. An unknown part of the population may not be included in the
sample.
3. Hence the results could not be generalized to the entire
population
An unknown part of the population may not be included in the sample.
Hence the results could not be generalized to the entire population