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DAVID M. COULTER, MD
The University of Utah Department of Pediatrics Eighth Avenue and C Street Salt Lake City, UT 84143

Am J Dis Child. 1991;145(3):249.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

Sir.—Brown's discussion¹ on the P value continues his elegant series of lucid dissertations on medical statistics. A brief clarification is needed, however, concerning the issue of multiple statistical tests and the risk of type I error. Such corrections to compensate for multiple tests on the same data set are important during "data dredging" expeditions, explorations of a data set in search of statistical differences that were not anticipated by the original study design or hypothesis. As Brown points out, there is one chance in 20 that any such comparison will be significant at the P=.05 level. The corrected P values also protect against the type I error, which can occur when "in examining the treatment means we notice a combination that we did not intend to test but which seems unexpectedly large."²

In contrast to the data dredger is the investigator who designs a prospective study . . . [Full Text PDF of this Article]

Footnotes
This department of AJDC is reserved for comment, criticism, observation, and discussion of "issues of current concern and importance for children's health." The Editor encourages our readers to express themselves on a variety of topics and issues. Further, we encourage the submission of unique and brief clinical and scientific observations that do not fulfill the criteria for original articles.

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