A type of in which each study subject receives the same series of but in a random order. Each subject serves as their own control in this type of study.
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About Cross-Over Trials
Randomly allocating patients to the comparison groups aims to reduce the chance of such biases occurring. It means that the groups start out with an equal chance of events occurring during the study, whether disease recurrence, side effects from or symptom relief. In other words, it increases the likelihood that any differences in outcome between the groups are caused by the test or treatment and not other factors.
Sometimes is done as a cross-over trial. This means that people are first randomised to A or B and then, after the outcome has been assessed, the groups cross over so that those who were receiving treatment A switch to treatment B and vice versa, and the outcomes are again measured. Of course, this type of trial can be done only if the outcomes are short and reversible — for example, to measure an ‘s effect on pain relief.