THESE are hard times for believers in evidence-based policy-making. Almost every day brings fresh news of initiatives that fly in the face of facts, from the mooted return of grammar schools and badger culling in the UK to the deluded and dangerous fantasies of Donald Trump. New Scientist has long argued that political decisions should be based on demonstrable evidence, and that randomised controlled trials (RCT) are the best way to gather that evidence. Put simply, you test one policy against another and see which one delivers the goods. So it is disappointing to report that medicine – the field that invented the RCT – often fails to live up to its own gold standard.