Mediation:
The Four Steps
David A. Kenny
davidakenny.net
Mediation Webinar
• Basics
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The Beginning Model
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The Mediational Model
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The Four Paths
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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.
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More Mediation
Webinars
• Indirect Effect
• Testing the Indirect Effect
• Causal Assumptions
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