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