The document discusses various sampling techniques used in research including probability sampling methods like simple random sampling, systematic sampling, stratified sampling, cluster sampling, and multistage sampling as well as non-probability sampling methods such as snowball sampling, convenience sampling, purposive sampling, quota sampling, and self-selection sampling. It provides details on how each method works and lists their advantages and disadvantages.

1. SAMPLING TECHNIQUES
PRESENTATION
BY
BELLO LAWAL DANCHADI
AT
CENTRE FOR ADVANCED MEDICAL RESEARCH AND TRAINING, (CAMRET).
USMANU DANFODIYO UNIVERSITY, SOKOTO.

2. Outlines
• Introduction
• Sampling design processes
• Types of sampling
• Advantages and disadvantages
• Summary
• References

3. Introduction
 Sampling techniques:
• Deciding how to select a sample that is representative of the population as a
whole (Khan, 2020).
Sampling:
• The process of through which sample is selected from the population (Khan,
2020).
 Sample:
• It is a unit that is selected from population
• Represents the whole population
• Purpose to draw the inference.
 Sampling frame:
• The actual list of population from which a sample is drawn from (Khan, 2020).

4. Sampling

5. Sampling design process

6. Probability sampling
Advantages:
• Minimal knowledge of population
needed
• Easy to analyze data
• Involves the random selection,
• Allow a researcher to make a strong statistical inference about the whole population
• Every member of the population has a chance of being selected.
• It is mainly used in quantitative research (Mccombesa, 2023).
1. Simple random sampling
• All subsets of the frame are given an equal probability.
• Equal chance of being selected
• It can be done using a random number generators
• It provides unbiased results but can be time-consuming.
Disadvantages:
• Low frequency of use
• Does not use researchers’ expertise
• Larger risk of random error

7. 2. Systematic sampling
• Alphabetically, order all units in the sampling frame
• Then every nth number on the list is selected
• n = sampling Interval
• After randomly selecting a starting point.
• It is straightforward to implement but may introduce bias if there is a pattern in the
data.
Advantages:
• Moderate cost; moderate usage
• Simple to draw sample
• Easy to verify
Disadvantages:
• Periodic ordering required (McCombesa, 2023)

8. 3. Stratified sampling
• Population is divided into two or more groups called strata.
• Based on the relevant traits (e.g., gender identity, age range, income, Job role).
• Subsamples are randomly/systematically selected from each strata.
• Subgroups are properly represented in the sample.
(Tam and Woo, 2020).

9. • Advantages:
• Assures representation of all groups in sample population
• Characteristics of each stratum can be estimated and comparisons made
• Disadvantages:
• Requires accurate information on proportions of each stratum
• Stratified lists costly to prepare (Tam and Woo, 2020).
4. Cluster sampling:
• The population is divided into subgroups (clusters) like families.
• A random selection of clusters is chosen.
• A simple random sample is taken from each cluster.
• It is useful when the population is geographically dispersed,
• But it may lead to less precision compared to other techniques. (Peven et al., 2019)

10. 5. Cluster sampling
Advantages:
• Can estimate characteristics of both cluster and population
Disadvantages:
• The cost to reach an element to sample is very high
• Each stage in cluster sampling introduces sampling error,
• The more stages there are, the more error there tends to be.

11. 5. Multistage sampling
• The population is divided into different stages, and a sample is selected at each stage.
• It starts with selecting larger clusters or groups from the population in the first stage.
• Then, within each selected cluster, smaller clusters or units are chosen in the second stage,
• This process may continue through several stages until the final sample units are selected.
• The final sample units can be individuals, households, or any other relevant units.
• Useful when the target population is large, geographically dispersed, or difficult to access.
Advantages:
• More Accurate
• More Effective
(McCombesa, 2023)
Disadvantages:
• Costly
• Each stage in sampling introduces sampling error
• The more stages there are, the more error there tends to be

12. Non probability sampling
• Individuals are selected based on non-random criteria, and not every individual
has a chance of being included.
• Often used in qualitative research (McCombesa, 2023).
• Units of the sample are chosen on the basis of personal judgment or convenience.
1. Snowball sampling
• The research starts with a key person and introduce the next one to become a chain
Advantages
• Low cost
• Useful in specific circumstances & for locating rare populations
Disadvantages
• Not independent
• Projecting data beyond sample not justified, (Elfil and Negida, 2017).

13. 2. Convenience sampling
• The process of including whoever happens to be available at the time…called
“accidental” or “haphazard” sampling.
• But there is no way to tell if the sample is representative of the population
(McCombesa, 2023).
Advantages
• Very low cost
• Extensively used/understood
Disadvantages
• Variability and bias cannot be measured or controlled
• Projecting data beyond sample not justified
• It can’t produce generalizable results.

14. 3. Purposive sampling
• Involves the researcher using their expertise to select a sample that is
most useful to the purposes of the research.
• Also called “judgmental” sampling.
Advantages
• There is a assurance of Quality response
• Meet the specific objective.
Disadvantages
• Bias selection of sample may occur
• Time consuming process. (McCombesa, 2023)

15. 4. Quota sampling
• The process whereby a researcher gathers data from individuals possessing
identified characteristics and quotas.
• You first divide the population into mutually exclusive subgroups (called strata)
and then recruit sample units until you reach your quota. (Omair, 2014).
• These units share specific characteristics, determined by you prior to forming your
strata.
• The aim of quota sampling is to control what or who makes up your sample.
Advantages
• Used when research budget is limited
• Very extensively used/understood
• No need for list of population elements.
(McCombesa, 2023).
Disadvantages
• Variability and bias cannot be
measured/controlled
• Time Consuming
• Projecting data beyond sample not
justified.

16. 5. Self-selection sampling
• It occurs when you allow each case usually individuals, to identify their desire to
take part in the research.
• Instead of the researcher choosing participants and directly contacting them,
people volunteer themselves (e.g. by responding to a public online survey).
Advantages
• More accurate
• Useful in specific circumstances to serve the purpose.
Disadvantages
• More costly due to Advertising
• Mass are left. (McCombesa, 2023)

17. References
• Elfil, M., & Negida, A. (2017). Sampling methods in clinical research: An educational review. Emergency,
5 (1), Article e52, 1–3.
• Firchow, P., & MacGinty, R. (2020). Including hard-to-access pop- ulations using mobile phone surveys
and participatory indica- tors. Sociological Methods & Research, 49(1), 133–160. Magnani, R., Sabin, K.,
Saidel, T., & Heckathorn, D. (2005). Review of sampling hard-to-reach and hidden populations for HIV
surveillance. AIDS, 19 (Suppl. 2), S67–S72.
• Omair, A. (2014). Sample size estimation and sampling techniques for selecting a representative sample.
Journal of Health Specialties, 2(4), 142–147.
• Peven, K., Purssell, E., Taylor, C., Bick, D., and Lopez, V. K. (2019). Breastfeeding support in low and
middle-income countries: Secondary analysis of national survey data, Midwifery, 82.
https://doi.org/10.1016/j.midw.2019.102601 Shorten, A., & Moorley, C. (2014). Selecting the sample.
Evidence Based Nursing, 17(2), 32–33.
• Tam, W., Lo, K., and Woo, B. (2020). Reporting sample size cal- culations for randomized controlled trials
published in nurs- ing journals: A cross-sectional study. International Journal of Nursing Studies, 102.
https://doi.org/10.1016/j.ijnurstu.2019 .1034
• McCombes, S. (2023). Sampling Methods | Types, Techniques & Examples. Scribbr. Retrieved July 9,
2023, from https://www.scribbr.com/methodology/sampling-methods/