Non- Probability Sampling & Its Methods

A detailed explanation of non-probability sampling and its methods have been covered. There are 4 types of non- probability sampling methods:
1. convenience sampling
2. purposive sampling
3. quota sampling (both controlled and uncontrolled)
4. snowball sampling (all 3 ways of performing)
Meaning with adequate examples, pros and cons have been covered
For and query or further information, Kindly contact:

Arpit Surana
https://www.linkedin.com/in/arpitsurana116/
[email protected]

1. NON - PROBABILITY SAMPLING

2. 2 Hello !! I am Arpit Surana [email protected] www.linkedin.com/in/arpitsurana116

3. NON – PROBABILITY SAMPLING Non-probability sampling is a sampling technique where the odds of any member being selected for a sample cannot be calculated . It’s the opposite of probability sampling, where you can calculate the odds. For example, one person could have a 10% chance of being selected and another person could have a 50% chance of being selected. It’s non-probability sampling when you can’t calculate the odds at all 3

4. 4

5. WHEN? WHY? TO USE NON-PROBABILITY SAMPLING This type of sampling can be used when demonstrating that a particular trait exists in the population. It can also be used when the researcher aims to do a qualitative, pilot or exploratory study. It can be used when randomization is impossible like when the population is almost limitless. It can be used when the research does not aim to generate results that will be used to create generalizations pertaining to the entire population. It is also useful when the researcher has limited budget, time and workforce. 5

6. Advantages Possibility to reflect the descriptive comments about the sample Cost-effectiveness and time-effectiveness Effective when it is unfeasible or impractical to conduct probability sampling PRONS & CONS Disadvantages Unknown proportion i.e. lack of representation of the entire population Lower level of generalization of research findings compared to probability sampling Difficulties in estimating sampling variability and identifying possible bias . 6

7. 7 4 Methods

8. CONVENIENCE SAMPLING 8 1 Also know as Accidental Sampling

9. In convenience sampling no inclusion criteria identified prior to the selection of subjects.  The sample is selected in anyway for the sake of easiness and convenience 9 9

10. 10

11. EXAMPLES Facebook polls Pepsi Challenge Feedback system in big companies 11

12. Advantages Simplicity of sampling and the ease of research Helpful for pilot studies and for hypothesis generation Data collection can be done in short duration of time Cheapest to implement PRONS & CONS Disadvantages Highly vulnerable to selection bias and influences beyond the control of the researcher High level of sampling error Studies that use convenience sampling have little credibility due to reasons above . 12

13. PURPOSIVE SAMPLING 13 2 Also known as judgment, selective or subjective sampling

14. The researchers or experts obtain a representative sample by using a sound judgment, which will result in saving time and money 14 14

15. 15

16. EXAMPLES TV reporters stopping certain individuals on the street in order to ask their opinions about GST on insurance (this can be asked to only to an educated man). A study of importance of exposure in colleges (this can be asked to only those students who has experienced exposure in college). 16

17. Advantages Cost-effective and time-effective Requires limited number of primary data sources One of the most t ime-effective sampling methods available PRONS & CONS Disadvantages Vulnerability to errors in judgment by researcher Low level of reliability and high levels of bias. Inability to generalize research findings . 17

18. QUOTA SAMPLING 18 3 It has two types controlled and uncontrolled

19. A method of gathering representative data from a group to ensure that sample group represents certain features of the population chosen by the researcher. 19 19

20. HOW TO PERFORM QUOTA SAMPLING 1. Dividing the population into specific groups Virgin Media employees in the UK as the sampling frame need to be divided into the following five groups according to their cultural background: European, Asian (India), Asian (China), Black (African) and Other 20 2. Calculating a quota for each group Suppose you take 30 representatives from each group making total of 150. 3. Determine specific condition(s) to be met and quota in each group Both genders, males and females need to be represented equally i.e. 15 each.

21. 21

22. Advantages Quota sampling is good when you are pressed for time, since primary data collection can be done in shorter time This sampling method can save costs and time. It can also be done in absence of sampling frame PRONS & CONS Disadvantages We can’t calculate sampling error and the projection of the research findings There is disproportionately represented in the final sample group It may suffer from researcher incompetency and/or lack of experience . 22

23. 2 TYPES QUOTA SAMPLING Uncontrolled sampling, in this the researcher is free to choose sample group members according to his/her will. 23 Controlled Uncontrolled Controlled sampling involves introduction of certain restrictions in order to limit researcher’s choice of samples.

24. 24

25. SNOWBALL SAMPLING 25 4 Also known as cold-calling, chain, chain-referral, and referral sampling.

26. Snowball sampling is where research participants recruit other participants for a test or study. It is used where potential participants are hard to find 26 26

27. INTERESING NAME !! It’s called snowball sampling because (in theory) once you have the ball rolling, it picks up more “snow” along the way and becomes larger and larger. 27

28. 28

29. EXAMPLES A study on investigating cheating on exams Company that involves primary data collection from employees of that company. Mostly used in taking surveys with the help of questionnaire. 29

30. 3 PATTERNS OF SNOWBALL SAMPLING Exponential non- discriminative snowball sampling The first subject recruited to the sample group provides multiple referrals. Exponential discriminative snowball sampling Subjects give multiple referrals, however, only one new subject is recruited among them. 30 Linear snowball sampling Formation of a sample group starts with only one subject and the subject provides only one referral.

31. Advantages The ability to recruit hidden populations The possibility to collect primary data in low cost It can be completed in a short duration of time A very little planning is required to start sampling process PRONS & CONS Disadvantages Oversampling can be done Respondents may be hesitant to ask all questions It is not possible to determine the actual pattern of distribution of population. It is not possible to determine the sampling error 31

32. REFERENCES https://research-methodology.net http://www.statisticshowto.com https://images.google.com/ 32

33. 33 THANKS! Any questions? Just comment me or you can find me at [email protected] www.linkedin.com/in/arpitsurana116/