Randomised controlled trials (RCTs)

These are the ‘gold standard’ of scientific studies because they are ‘controlled’. This means that steps have been taken to try to eliminate things that might have an influence beyond the specific thing being studied (as opposed to epidemiological studies). 

The conclusions of a good quality RCT, then, can be quite a strong basis for claims. 

RCTs are most often used to examine the effect of a drug or treatment on a person’s health. In RCTs for medical treatments, participants are separated into two groups; one is given the intervention and the other is given either a placebo (a dummy treatment that looks like the real one being tested, like a pill made of sugar) or the current best treatment, to find out whether the new treatment really is having an effect, and work out how big that effect is. 

RCTs can be carried out in other areas of life too (for example, to test different teaching methods or new policies to tackle crime), though it is not always possible, practical or ethical to carry one out.

Tags: evidence

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