3.5.2 Pre-post test studies
Another method for evaluating the effectiveness of a therapy is to use a pre-post test design. This is where a group of people is assessed before and after a programme of intervention. Ideally, these people would be matched to a control group who are also tested twice, but do not receive the same (or any) intervention during that period. However, as with randomised controlled trials, there are ethical issues if it becomes clear that the intervention is having an adverse affect on the experimental group. Even if the intervention is successful, there may be ethical issues as the control group could be seen as ‘disadvantaged’ by not receiving the intervention. Finally, it is always important to assess the long-term effects of any intervention programme to see if the apparent benefits are sustained long after the study has concluded.