Understanding Moderation and Mediation in Predictive Analysis

1. Chapter 13 Mediation Class 8 Spring 2017 Ang &Huan (2006)

3. 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

4. Moderation Analyses: Regression P: Alcohol use M: Gender Depression Alcohol Use X Gender M F

5. 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

6. Mediation: Baron & Kenny (1986)The Beginning Model c Y X

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

8. Baron and Kenny procedure • 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. 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.

10. Ang & Huan(2012) b a c

11. Ang & Huan(2012) Depression b a c Suicidal Ideation Academic stress C”

14. Mediation Model Ang & Huan (2006)

15. 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%

16. 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%

17. Mediation VS Indirect Effects

18. Class Example Friends’ Drinking b a c Self-Reported Drinking Drinking Attitudes

20. Path Analyses

21. SEM Model

22. Person Centered Approach Identify groups of people who are similar and different Cluster Analysis Latent Class Profile Analyses Growth Mixture Analyses

24. Latent Profile/Class Analyses • Identify subgroups of people based on individual characteristics • Profile - Continuous measure • Class- Categorical measure • Calculate probabilities of being in each group-

25. Growth Mixture Modeling