> "drug A show 50% vs. 20% efficacy vs. placebo and drug B showed 70% vs. 40% efficacy vs. placebo" Which raises a further (or more basic) confounding factor:

> "drug A show 50% vs. 20% efficacy vs. placebo and drug B showed 70% vs. 40% efficacy vs. placebo" Which raises a further (or more basic) confounding factor: the placebo effect isn't fixed. It does vary between trials and even appears to be steadily increasing in potency over time. [1] So first-to-market drugs have an added advantage when naively considering "improvement vs placebo" -- as their test were run years ago, when the placebo effect itself was a weaker opponent. [1] http://www.wired.com/medtech/drugs/magazine/17-09/ff_placebo_effect?currentPage=all http://www.wired.com/medtech/drugs/magazine/17-09/ff_placebo...