The published literature contains numerous reports of clinical studies. A problem in their interpretation is that studies in which the observed efficacy of the treatment is high are much more likely to be reported than those in which the observed efficacy is average or poor. This phenomenon has had the consequence of generally discrediting the reliability of the literature, especially that of non-randomized studies.
In this paper a model is developed which permits estimation of the potential magnitude by which the reported efficacy of a treatment might be inflated. This quantity is termed the publication bias. The magnitude of the bias depends on the sample size of the study and the number of similar studies conducted concurrently. Tabulated values of the bias are presented, permitting easy computation.
The new measure may have potential use for physicians in clinical decision making in that it characterizes the reliability of results from a specific published study, especially when there are no definitive randomized studies. However, correction of publication bias in this manner is not a substitute for a well controlled or a randomized study. The technique merely assists in the interpretation of available evidence from the literature. Moreover, it must be used with due caution in recognition of the assumptions and approximations involved in the calculation.