Large scale randomised evidence of moderate benefits

Over the past half century there has been a vast proliferation first of randomised trials and now of meta-analyses, both of which (if appropriately analysed) can avoid bias. But to get medically reliable answers to previously unanswered questions about life or death treatment decisions it isn't enough just to avoid bias. We must also ensure that we are not seriously misled by the play of chance, and often the only way to do this reliably is to get appropriate analyses of really large scale randomised evidence.1

At present, many wrong, or at least unreliable, therapeutic answers are being generated by non-randomised “outcomes research,” by small randomised studies, by small meta-analyses, and by statistically inappropriate analyses. Moreover, even when large scale randomised evidence is available, wrong conclusions can be drawn from unduly selective emphasis on particular trials or subgroups—and such “selection biases” can cause even greater errors when there is only a limited amount of evidence to review.

Over the past 50 years randomisation has already delivered reliable answers to some important questions and it offers the promise of reliable answers to many more. For that promise to …