Some treatment comparisons are designed to find out if a treatment can work under ideal circumstances, for example, with people who are most likely to benefit and most likely to comply (e.g. young adults who have had stroke and need to get back to work), and with highly trained practitioners who deliver the treatment exactly as intended.
These comparisons, which are sometimes called efficacy studies, may not reflect what happens under usual circumstances.
REMEMBER: Ask whether treatment comparisons were conducted under ideal circumstances. The results of such studies may overestimate the benefits of the treatment when used under more usual circumstances.