Table 5: Research design categories and the specific needs they each address
Status of knowledge regarding problem Type of research question Appropriate research study design
Knowing that a problem exists but knowing little about its characteristics or possible causes.
  • What is the nature/
  • magnitude of the problem?
  • Who is affected?
  • How do the affected people behave?
  • What do they know, believe, think about the problem and its causes?

Descriptive studies:

    Cross-sectional surveys
Suspecting that certain factors contribute to the problem (or are associated with it)
  • Are certain factors indeed associated with the problem? (e.g. lack of pre-school education related to low school performance? Is low-fibre diet related to carcinoma of the large intestine?)

Analytical (Comparative) studies:

  • Cross-sectional comparative studies
  • Case control studies
  • Cohort studies
Having established that certain factors are associated with the problem: Establishing the extent to which a particular factor causes or contributes to the problem
  • What is the cause of the problem?
  • Will the removal of a particular factor prevent or reduce the problem? (e.g. stopping smoking, providing safe water).
  • Cohort studies Experimental or quasi-experimental studies
Having sufficient knowledge about cause(s) to develop and assess an intervention that would prevent, control or solve the problem
  • What is the effect of a particular intervention/strategy? (E.g. treating with a particular drug; being exposed to a certain type of health education)
  • Which of two alternate strategies gives better results?
  • Which strategy is most cost-effective?
  • Experimental or quasi-experimental studies