Post on 04-Jan-2016
Mediation: The Four Steps
David A. Kennydavidakenny.net
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Mediation Webinar
• Basics
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The Beginning Model
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The Mediational Model
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The Four Paths
• X Y: path c
• X M: path a
• M Y (controlling for X): path b• X Y (controlling for M): path c′
(standardized or unstandardized)
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In the 1980s Different Researchers Proposed a Series
of Steps to Test Mediation
• Judd & Kenny (1981)
• James & Brett (1984)
• Baron & Kenny (1986)
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Steps
• Step 1: X Y (test path c)• Step 2: X M (test path a)• Step 3: M (and X) Y (test path b)• Step 4: X (and M) Y (test path c′)
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Differences in the Three Approaches
• James & Brett assuming complete mediation estimate Step 3 without controlling for X whereas both Judd & Kenny and Baron & Kenny control for X.
• Judd & Kenny and James & Brett require all four steps whereas Baron & Kenny do not require Step 4.
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Steps Incredibly Popular with Practitioners
• Suggested a straightforward way of testing mediation using a widely available estimating method.
• Very often lead to a successful result: Some sort of mediation was indicated.
• Very widely adopted and eventually the expectation was for some sort of mediational analysis.
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References
• Judd, C. M., & Kenny, D. A. (1981). Process analysis: Estimating mediation in treatment evaluations. Evaluation Review, 5, 602-619.
• James, L. R., & Brett, J. M. (1984). Mediators, moderators and tests for mediation. Journal of Applied Psychology, 69, 307-321.
• Baron, R. M., & Kenny, D. A. (1986). The moderator-mediator variable distinction in social psychological research: Conceptual, strategic and statistical considerations. Journal of Personality and Social Psychology, 51, 1173-1182. 10
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More Mediation Webinars
• Indirect Effect
• Testing the Indirect Effect
• Causal Assumptions