A meta-analytic review of leadership impact research: Experimental and quasi-experimental studies

In this study we set out to conduct a comprehensive quantitative research analysis of literature reporting results on the causal impact of leadership by focusing on examining what we refer to as ‘leadership interventions.’ We defined leadership interventions as those studies where the researcher overtly manipulated leadership as the independent variable through training, assignment, scenario or other means. Our focus included both examining experimental and quasi-experimental as well as lab and field studies conducted in public and private organizations. Our goal was to address a simple question: do leadership interventions have the intended impact and if so to what degree? We conducted a comprehensive review of the published and unpublished literature and uncovered 200 lab and field studies that met our criterion as leadership intervention studies. We report here the findings of a series of metaanalyzed effects comparing the relative impact of leadership interventions across intervention types, leadership theories, and several common dependent variables. Overall, leadership interventions produced a 66% probability of achieving a positive outcome versus a 50–50 random effect for treatment participants, but this effect varied significantly when assessing moderators such as type of leadership theory. © 2009 Elsevier Inc. All rights reserved.