Understanding the practical advantages of modern ANOVA methods.

Examined the fundamental problems associated with standard hypothesis testing techniques. This article explains why many articles have failed to detect problems due to nonnormality and discusses the basics of modern methods aimed at correcting these problems. Based on hundreds of published articles, it is now known that when groups differ, the analysis of variance (ANOVA) F test and related techniques that assume normality and homoscedasticity (equal variances) can perform poorly. In practical terms, if researchers interested in clinical child and adolescent psychology want to detect important differences among groups and accurately assess how the groups differ, and by how much, modern technology has much to offer. In fact, even highly nonsignificant results based on an F test can become significant. Moreover, modern methods offer improved control over the probability of a Type I error and more accurate confidence intervals.