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May 1986

Establishing Therapeutic Equivalency: What Is a Clinically Significant Difference?

Author Affiliations

Toronto General Hospital Toronto, Ontario, Canada M5G 1L7; Hamilton, Ontario

Arch Intern Med. 1986;146(5):861-862. doi:10.1001/archinte.1986.00360170057006

Clinical trials produce results. From these results investigators will draw one of two conclusions: "experimental" and "control" treatments produce different outcomes (a "positive" conclusion), or experimental and control treatments produce similar outcomes (a "negative" conclusion). Because trials are always performed on a subsample of all patients, these conclusions may be wrong. We may draw the "false-positive" conclusion that the experimental treatment works, when, in truth, it does not; and we may draw the "false-negative" conclusion that the experimental treatment does not work, when, in truth, it does.

When the risk of drawing a false-positive conclusion (a type I error) is unacceptably high, it is tempting for investigators to conclude that the experimental treatment does not make a difference. However, statisticians have heightened our awareness of the illogic of this conclusion. A high risk of a false-positive conclusion does not guarantee a low risk of a

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