Glossary
Randomised controlled trial.
Direct answer
A randomised controlled trial allocates participants by chance to a treatment group and a comparison group. Randomisation spreads known and unknown differences evenly on average across the groups. A difference measured at the end can therefore be attributed to the treatment rather than to the way the groups were assembled.
What matters is not the draw alone but concealed allocation: whoever enrols a subject must not know the next group, or selection creeps back in. It matters equally that every allocated subject stays in the analysis, dropouts included. If one group empties along the way, part of the benefit of randomisation is lost again.
In horses, randomised trials stay small: a few dozen animals per arm already counts as generous, whereas human trials can enrol thousands. Researchers often randomise limbs or treatment periods instead of whole animals. That spares subjects, but it demands an analysis that accounts for two measurements on the same horse not being independent of each other.
Control groupBlinding (single and double)PlaceboLevel of evidence
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