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Chapter 10 Mediation

Chapter 10 Mediation. Class 6 Spring 2013 Ang & Huan (2006) . Moderator vs. Mediator. Moderator variable (“ separator ”) When or for whom a variable X most strongly predicts an outcome (criterion) variable Y (strength and direction + or -) Mediator

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Chapter 10 Mediation

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  1. Chapter 10 Mediation Class 6 Spring 2013 Ang &Huan (2006)

  2. Moderator vs. Mediator Moderator variable (“separator”) When or for whom a variable X most strongly predicts an outcome (criterion) variable Y (strength and direction + or -) Mediator The mechanism by which a predictor causes or explains the outcome

  3. Moderation Analyses: Regression Predictor Moderator Outcome Predictor X Moderator High M Low M

  4. Mediation Establishes Howor Why a variable causes or predicts the criterion (or outcome) variable. Mediator is the mechanism by which predictor causes or explains the outcome Predictor -------------------------------Outcome Predictor --------- Mediator---Outcome Parent Drinking----F. Conflict -Low Self Esteem

  5. MediationThe Beginning Model c Y X

  6. The Mediational Model M b a c' Y X

  7. The Mediational Model Family Conflict b a C’ Parent Drinking Low Self-Esteem

  8. Baron and Kenny Steps • X  Y (test path c) • M (test path a) • M (and X)  Y (test path b) • X (and M)  Y (test path c′ ) Analyses 3 and 4 use the same regression equation.

  9. Hierarchical regressions analyses to test mediation Reg. 1PredictorOutcome Prnt. Drinking ------ c ---- Low Self Esteem Reg 2 PredictorMediator Prnt. Drinking ------ a ------ Family Conflict Reg 3 MediatorOutcome Family Conflict ----- b ----- Low Self-Esteem (controlling for Predictor – Parent Drinking) Reg 3 Predictor----Mediator ------Outcome Prnt. Drinking -- Fam. Conflict ------  Low Self Esteem C’

  10. Regressions Mediation Analyses:Criterion:OutcomeLow Self EsteemReg 1(Path c) Reg 1B β ΔR2 R2

  11. Hierarchical Regression Mediation Analyses: Criterion: Low Self Esteem (Paths b and C’)Reg 3B β ΔR2 R2

  12. Hierarchical Regression Mediation Analyses: Criterion: Low Self Esteem (Partial Moderation Reg 3A) B β ΔR2 R2

  13. Sobel Test Calculatorhttp://www.psych.ku.edu/preacher/sobel/sobel.htm Whether the indirect effect of the predictor on the criterion via the mediator is significantly different from zero Numbers needed a = raw (unstandardized) regression coefficient for the association between predictor and mediator. sa = standard error of a. b = raw coefficient for the association between the mediator and the outcome (when the predictor is also a predictor of the DV). sb = standard error of b.

  14. Ang & Huan(2012) b a c

  15. Ang & Huan(2012) Depression b a c Suicidal Ideation Academic stress

  16. Mediation Model Ang & Huan (2006)

  17. Strength of Mediated Effect Sobel Test- Indicated if change in academic stressBs from Path c to path c’ is statistically significant Shrout & Bolger (2002) Proportion of relation of academic stress to suicide ideation that is mediated by depression Calculated from the unstandardized Bs for paths ab& c; requires a sample size of about 500 ab/c = ( ) ( )/ ( ) = ( ) / ( ) = .7390 = 74%

  18. Strength of Mediated Effect Sobel Test- Indicated if change in academic stressBs from Path c to path c’ is statistically significant Shrout & Bolger (2002) Proportion of relation of academic stress to suicide ideation that is mediated by depression ab/c = (.12) (2.71)/.44 = .3252/.44 = .7390 = 74%

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