<P>This guide lays out the computational methods for &quot;d&quot; with a variety of designs including factorial ANOVA, ANCOVA and repeated measures ANOVA; &quot;d&quot; divides the observed effect by the standard deviation of the dependent variable. Throughout, the computations are illustrated on the same data, a comprehensive set of simulated observations on air traffic controllers. The authors also raise important theoretical issues including a discussion of &quot;off-factor&quot; in arriving at effect size as well as questions of research practice. </P>