Annals of emergency medicine
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In the analysis of a clinical trial an investigator may fail to discern a statistically significant difference in outcome between control and experimental groups, when in fact one exists. Failure to demonstrate such a difference when it actually exists is known as "type II" error, and its probability of occurring is termed "beta." The purpose of our study was to determine the distribution of beta errors in negative trials in the Journal of the American College of Emergency Physicians (JACEP) (1972-1979) and Annals of Emergency Medicine (1980-1984). All negative comparative clinical trials appearing in JACEP and Annals from volume 1 (1972) to volume 13 (1984) were surveyed and were eligible for inclusion in the study. ⋯ Only one of the trials (7.1%) addressed the issues of beta errors and sample size determination. In the remaining 13 negative trials, the calculated beta error ranged from .60 to .97. For the endpoints analyzed, a sample size of up to 450 times larger than that used would have been required to detect a clinically important difference.(ABSTRACT TRUNCATED AT 250 WORDS)