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Chapter 13 Mediation. Class 8 Spring 2017 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 13 Mediation Class 8 Spring 2017 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 The mechanism by which a predictor causes or explains the outcome
Moderation Analyses: Regression P: Alcohol use M: Gender Depression Alcohol Use X Gender M F
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
The Mediational Model M b a c' Y X
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.
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.
Ang & Huan(2012) b a c
Ang & Huan(2012) Depression b a c Suicidal Ideation Academic stress C”
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%
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%
Class Example Friends’ Drinking b a c Self-Reported Drinking Drinking Attitudes
Person Centered Approach Identify groups of people who are similar and different Cluster Analysis Latent Class Profile Analyses Growth Mixture Analyses
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-