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Understanding autism
Understanding autism

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3.3 Controlled studies and randomised control trials

A controlled study is a more rigorous and formal evaluation of an intervention similar to a research experiment (see Week 1 [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] ). The study typically involves two groups of participants on the autism spectrum, both larger than those used in pilot and small-scale evaluations. One group (the experimental or intervention group) receives the intervention, and the other (the control group) does not, or they receive another intervention already known to have some effect. The latter procedure is known as ‘treatment as usual’.

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 outcome measure.

Activity 2 Principles of controlled evaluation

Timing: Allow about 5 minutes

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.

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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 randomised control trial (RCT) refers to a full-scale controlled evaluation involving random allocation to intervention and ‘treatment as usual’ groups, and a relatively large number of participants. RCTs are widely used to evaluate new medical interventions, and are also considered the ‘gold standard’ in the autism field. But to date, few evaluations of autism interventions have been evaluated as far as the RCT stage. We will consider why next.