Sample size in occupational mortality studies.

In 1980, the Occupational Safety and Health Administration asserted that "non-positive human studies" would be considered in reviews of evidence only if in a study the "group of exposed subjects was large enough for an increase in cancer incidence of 50% above that in unexposed controls to have been detected at any of the predicted sites." The concepts of statistical testing and power in occupational mortality studies are reviewed, and studies …