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Abstract #19234 Published in IGR 3-1
The negative study
Brown MMEvidence-Based Eye Care 2001; 2: 71-73
In this paper, the author considers the value of negative outcomes. If the result is negative, first of all we should be aware of the power of the study. The power of a study is defined as 1-B (1 minus the type II error). A type II error occurs when we falsely assume that there is no difference between treatment groups, while there is in fact a difference. In essence, we fail to detect the real difference that exists. A type II error of 10% would therefore yield a power of 90%. The most common cause of type II error is a lack of a sufficient number of patients in a study. If that is not the case and the result is negative, the study is at least as important as a positive study. The author gives some examples of major studies with negative results. She also presents us with some calculations on the Age Related Eye Disease Study (AREDS). The calculations really compare the costs of the study and the savings that may occur if patients stop taking anti-oxidants and zinc. The cost of taking anti-oxidants and zinc is close to $ 700 million. The costs of the study are calculated to be some $ 20 million. If the study is negative, some $ 680 million could be saved. However, although a negative result is not as glamorous as a positive one, the study outcome is just as important.
