Hopefully obvious, but some of this stuff also applies to A/B testing.
Yet in the 1950s the usual technique was to give a new treatment to the patients whom it was thought would most benefit from it. It frequently happened that those were the patients whose chances of recovery were the best in any case, under the existing treatments as well as the new one. The result was all too often that new treatments were thought to be better than old ones but in fact were not.
Yet in the 1950s the usual technique was to give a new treatment to the patients whom it was thought would most benefit from it. It frequently happened that those were the patients whose chances of recovery were the best in any case, under the existing treatments as well as the new one. The result was all too often that new treatments were thought to be better than old ones but in fact were not.