Clinical trial subgroup analysis: How to evaluate post hoc tests for significance in failed clinical trialsIf you spend enough time following biotech, youll encounter a common situation: A big clinical trial fails, but the company points to a glimmer of an effect in a subset of patients. The next thing you know, the firm is launching a big follow up study focused on that subgroup, often accompanied by a big fundraising push. There are good reasons to be skeptical of these follow up studies, but they can yield important insights that are ultimately green