The use of epidemiological tools in conflict-affected populations: open-access educational resources for policy-makers

Table of Contents

1. Welcome
2. Introduction: Epidemiology in crises
3. Ethical issues in data collection
4. Need for epidemiologic competence
5. Surveys - Introduction
6. Surveys - Description of sampling methods
   1. Sampling unit
   2. What is sampling?
   3. Why do sampling?
   4. Goal of sampling
   5. Simple random sampling
   6. Systematic random sampling
   7. Choosing between simple and systematic sampling - Quiz
   8. Cluster sampling
   9. Sampling - Additional resources
7. Surveys - Sampling error, bias, accuracy, precision, & sample size
8. Surveys - Resources required for surveys
9. Surveys - Critiquing survey reports
10. Surveillance - When to do surveillance
11. Surveillance - Methods
12. Surveillance - Common problems
13. Programme data
14. Rapid assessment
15. Mortality - Indicators and their measurement
16. Mortality - Data sources
17. Mortality - Interpretation and action
18. Nutrition - Introduction and background
19. Nutrition - Indicators and their measurement
20. Nutrition - Data sources
21. Nutrition - Interpretation and action
22. Health services
23. Vaccination programmes
24. Water supply, sanitation, and shelter
25. Violence
26. Presentation of results
27. Formulating conclusions and recommendations
28. Dissemination and action

Goal of sampling

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Other than saving time and money, what is the goal of sampling for a survey?

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What is necessary to achieve this goal?

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We don't really care what the health and nutrition status of the people in the survey sample is. They usually make up a relatively small proportion of the total population. What we really need to know is the health and nutrition status of the entire population which is estimated by measuring indicators and outcomes in a sample of the population.

Remember this point!!

Regardless of the sampling method, if the sample is not representative, it will give you misleading information about the population - so misleading, in fact, that the survey may do more harm than good and add to the confusion rather than enhance clarity.

Whenever you are faced with different ways of doing sampling (should I do it this way or that way?), choose the way that enhances or increases representativeness.

In subsequent pages, three different methods of random sampling will be discussed. All three methods will, if done correctly, result in a representative randomly selected sample. The important point is not the sampling method used, but how correctly the sampling method is used.