The sample may be large while the slice of life remains narrow.

A study with a huge number of participants can still be drawn from a very narrow world. All from one country, one platform, one age band, one kind of institution. Size protects against random error and does nothing at all about a systematically limited pool.

Rather than being reassured by the number of participants, ask who they were. Then ask whether you or the people you are deciding about resemble them. Large and narrow is a common combination, and it is more misleading than a small study that is honest about its scope.