When ab ≠ c - c′: Published errors in the reports of single-mediator models

Abstract

Accurate reports of mediation analyses are critical to the assessment of inferences related to causality, since these inferences are consequential for both the evaluation of previous research (e.g., meta-analyses) and the progression of future research. However, upon reexamination, approximately 15 % of published articles in psychology contain at least one incorrect statistical conclusion (Bakker & Wicherts, Behavior Research Methods, 43, 666-678 2011), disparities that beget the question of inaccuracy in mediation reports. To quantify this question of inaccuracy, articles reporting standard use of single-mediator models in three high-impact journals in personality and social psychology during 2011 were examined. More than 24 % of the 156 models coded failed an equivalence test (i.e., ab = c - c′), suggesting that one or more regression coefficients in mediation analyses are frequently misreported. The authors cite common sources of errors, provide recommendations for enhanced accuracy in reports of single-mediator models, and discuss implications for alternative methods. © 2012 Psychonomic Society, Inc.