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Blinding, and what the control group receives

Who knows which group a participant is in, and what the control group receives, shape every trial result. Blinding keeps knowledge of assignment from changing behavior or measurement. A home-visit program can't hide itself from the families it visits, but outcome assessors and analysts can almost always be blinded, and objective measures can replace self-report. The comparator matters just as much: placebo, active treatment, standard care, dose comparison or a waiting list. An intervention that beats a weak comparator may tie a strong one, because every effect is relative to its comparison.

Also covered: single, double and triple blinding · analyst blinding · placebo and active controls · waiting-list controls