The Physician

John P. A. Ioannidis, a professor of medicine at Stanford University, as told to Brooke Borel. Credit: Bud Cook

The answer to questions about human life isn't a certain thing, like measuring how a stone drops to the ground in exactly so many seconds. If it were, it probably would not be life. It would be a stone. Within biomedicine, it's tricky finding out if an effect is real—there are different standards across different fields. Not all tools will work for every question, and there are different levels of complexity for what we know before we even start a study.

Still, the one core dimen