The computation and reporting of effect size estimates is becoming the norm in many journals in psychology and related disciplines. Despite the increased importance of effect sizes, researchers may not report them or may report inaccurate values because of a lack of appropriate computational tools. For instance, Pierce, Block, and Aguinis (2004) provided examples of articles published in prestigious journals such as "Psychological Science", "Developmental Psychology", "Journal of Educational Psychology", and "Journal of Abnormal Psychology", in which researchers erroneously reported partial eta-squared values as representing classical eta-squared values. Here, the authors discuss the reasons behind the inaccuracy of values. One likely reason is that most commercially available statistical software packages provide only a limited number of effect-size estimates. Among other things, the authors discuss the effect-size metric f[squared], which is used in moderated multiple regression (MMR) to describe the strength of a moderating effect.