R. M. Baron and D. A. Kenny (1986) defined mediation and described how to perform statistical tests of mediation hypotheses. Their approach to testing mediation has been used extensively in the nursing literature. However, many statisticians have identified problems with the Baron and Kenny approach.
The aim of this paper is to critically evaluate alternative approaches to testing mediation.
The Baron and Kenny approach and its shortcomings are briefly reviewed. A critical analysis of 17 alternate methods in three categories is then presented: (a)causal steps, (b) difference in coefficients, and (c) product of coefficients. The evaluation focuses on Type I error rate control, power, ease of computation, and versatility of use.
Of the methods that control Type I error rate adequately, the joint significance test of α and β, the asymmetric distribution of products test, and the test of the products using the percentile bootstrap method are the most powerful tests of mediation. Of these three, the joint significance test of α and β is superior due to its computational ease and versatility of use.
Knowledge development in nursing will benefit from continued research testing mediation models. Nurse researchers could move beyond the Baron and Kenny approach to utilize more robust tests of mediation.
Melanie R. Krause, MS, RN, is Predoctoral Fellow, School of Nursing; Ronald C. Serlin, PhD, is Professor Emeritus, Department of Educational Psychology; Sandra E. Ward, PhD, RN, FAAN, is Helen Denne Schulte Professor of Nursing, School of Nursing; (Rachel) Yaffa Zisk Rony, PhD, MPH, RN, is Postdoctoral Fellow, Department of Family Medicine; Miriam O. Ezenwa, MS, RN, is Predoctoral Fellow, School of Nursing; and Florence Naab, MS, RN, is Doctoral Student, School of Nursing, University of Wisconsin-Madison.
Accepted for publication February 11, 2010.
(Rachel) Yaffa Zisk Rony is now at Henrietta Szold Hadassah-Hebrew University, School of Nursing, and Hadassah University Hospital, Jerusalem, Israel.
This work was supported by a John A. Hartford Foundation Building Academic Geriatric Nursing Capacity Predoctoral Scholarship (AAN 08-131) and F31NR010039 to Melanie R. Krause, R01 NR03126 and P20 NR008987 to Sandra E. Ward, T32PH10010 to Rachel Yaffa Zisk Rony, and F31NR010820 to Miriam O. Ezenwa.
Corresponding author: Sandra E. Ward, PhD, RN, FAAN, School of Nursing, University of Wisconsin-Madison, Box 2455, Clinical Sciences Center, K6/3, 600 Highland Avenue, Madison, WI 53792. (e-mail: email@example.com).