The Controlled Trial

A controlled trial tests a treatment or intervention by comparing a group that receives it against a comparison group, as similar as possible in every other respect, that does not, so that any difference in outcome can be attributed to the intervention rather than to chance or to differences between the groups. One of the earliest documented examples is James Lind's 1747 shipboard comparison of six pairs of sailors with scurvy, each pair given a different treatment, with the pair given citrus fruit recovering; the modern randomized controlled trial, assigning subjects to groups by chance rather than by the experimenter's choice, developed in the twentieth century and is now medicine's standard for testing whether a treatment actually works.