Figure 1.

Illustration of the Efficacy Paradox. Treatment x can have a larger overall effect than treatment y, although only treatment y shows a sizeable and significant specific treatment effect; specific = specific component of treatment; non-specific = non-specific component of treatment; regression = regression to the mean, natural regression of the disease; artefacts = measurement artefacts that mimic therapeutic effects; non-specific effects, artefacts, and regression comprise the placebo effect in RCTs.

Walach et al. BMC Medical Research Methodology 2006 6:29   doi:10.1186/1471-2288-6-29
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