3.3 Controlled studies and randomised control trials
Ideally the two participant groups in the study should be matched on criteria such as age, IQ or severity of symptoms, before the intervention begins. After the intervention period, the two groups are compared to see if there are any differences. This comparison requires a specific measure of the skills or behaviours that the intervention is designed to target, known as the
Activity 2 Principles of controlled evaluation
In a controlled study, one possible way to evaluate the effect of the intervention is for the control group to receive no intervention at all. However, the ‘treatment as usual’ procedure just outlined is more usual. Suggest one or more reasons for this.
Offering an alternative ‘treatment as usual’:
- reduces the likelihood that parents, or control participants themselves, will lack motivation to be involved. This could affect recruitment, and/or the outcomes in the control group
- helps to address ethical issues: there is a good chance that everyone will gain some benefit from the study, whether in the new intervention or in the ‘treatment as usual’ group
- enables the new intervention to be compared with existing interventions, to see if it is more or less effective.
Another ideal procedure for a controlled study is that participants are assigned randomly to treatment and control groups – much like drawing numbers out of a hat. This avoids factors which might bias the outcomes, for instance, that the participants in the intervention group are more high-functioning than those in the control group. The term