: This essay is an exploration of the problem of applying research results based on large numbers to the individual child and the child's development. The main argument of the article is that the results of populationbased studies are not directly relevant to individuals and that attempts to apply findings to individual children are often based on misunderstandings about measurement, statistics, and the processes of development. Although research into the relationship of elevated lead levels and cognitive development serves as a specific context for exploring these general issues, the issues are germane to many areas of development and many potential influences. The goal of the article is to provide an explicit discussion of scientific issues presented to members of the public and potential sources of confusion.
(C) 1999 Lippincott Williams & Wilkins, Inc.