Experimental researchers routinely use regression in order to control for pre-treatment covariates. This practice has become controversial in the wake of recent demonstrations showing that this type of regression is prone to bias in small samples. Bias may even remain when units are sampled from...

If the publication decisions of journals are a function of the statistical significance of research findings, the published literature may suffer from "publication bias." This paper describes a method for detecting publication bias. We point out that to achieve statistical significance, the...