Effect magnitude: A different focus

The role of measures of effect magnitude in the research enterprise is examined. Measures of effect magnitude are used for four purposes: (a) to estimate the sample size required to achieve an acceptable power, (b) to integrate the results of empirical research studies in meta-analyses, (c) to supplement the information provided by null hypothesis significance tests, and (d) to determine whether research results are practically significant. The advantage of focusing on effect magnitude and practical significance instead of statistical significance and p values is illustrated with an example. (c) 2006 Elsevier B.V. All rights reserved.