14.4 Selecting the appropriate study type to investigate a particular problem
The choice of your study design may depend on the following factors:
- type of problem
- knowledge already available about the problem
- resources available for the study.
For example, as we said earlier, cohort studies are very expensive because they have to follow-up a large number of individuals over a long period of time until the results become clear. Some possible investigations, and the type of study design which would be most suitable in each case, are shown in Table 14.1.
| Investigation | Appropriate study type |
|---|---|
| Investigation of current practice, e.g. treatment of fever at a household level | Cross-sectional study |
| Investigation of a disease which is rare in the community, e.g. breast cancer | Case-control study |
| Investigation of multiple exposures to a single disease agent, e.g. HIV/AIDS | Case-control study |
| Investigation of outcomes of an intervention, e.g. protecting a water source (Figure 14.5) and observing the number of diarrhoea cases in a community over time | Cohort study |
Figure 14.5 Installation of a protected water source should have an impact on the number of cases of diarrhoea. (Photo: Richard Adam)
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14.3.5 Cohort studies