What is Experimental and Quasi-Experimental Evaluation?
• Experimental and quasi-experimental research methods provide valid and reliable evidence about the relative effectiveness of a policy intervention compared with other policy interventions, or doing nothing at all (i.e. the counterfactual). • The purest form of experimental method is the randomised controlled trial (RCT – sometimes called the random allocation method of evaluation). • Randomised control trials deal with the problem of other possible factors influencing an outcome by exposing an experimental group of people, and a non-experimental (i.e. control) group of people to exactly the same factors except the policy, programme or project under investigation. • The allocation of people to the experimental policy intervention, or to the control (i.e. no intervention) situation, is done purely on the basis of chance (i.e. randomisation). Randomisation may be of individuals or of units (e.g. hospitals, schools), clusters, or whole areas. • Randomisation does not guarantee that the e
