Combining independent p values: Extensions of the Stouffer and binomial methods

The Stouffer z method, and other popular methods for combining p values fro m independent significance tests, suffer from three problems: vulnerability to criticisms of the individual studies being pooled, difficulty in handli ng the "file drawer problem," and vague conclusions. These problems can be reduced or eliminated by supplementing a test of combined probability with a variety of new analyses described here. Along with other advantages, thes e analyses provide a way to address the file drawer problem without malting limiting assumptions about the nature of studies not included in the poole d analysis. These analyses can supplement a traditional meta-analysis, yiel ding conclusions not provided by widely used metaanalytic procedures.