Psychology 202b Advanced Psychological Statistics, II March 29, 2011

Path Analysis First, a brief discussion of moderation and mediation. Assessing mediation.

Moderation We say that a one variable moderates the relationship between another pair of variables if the correlation (or regression) of the other two variables depends on the moderator. In other words, moderation is a synonym for interaction. Example from last class.

Mediation We say that one variable (M) mediates the relationship between another pair of variables (X and Y) if the direct path from X to Y diminishes or becomes zero when M is added as an intervening variable in the model. Nice discussion at

Mediation (cont.) Note that use of the Sobel test is becoming increasingly controversial. Anyone planning to use this sort of analysis should also look into bootstrap approaches. Advantages: greater power, freedom from distributional assumptions, can handle multiple mediators.

Some Vocabulary Related to Path Models Exogenous variables are variables that only have paths leading away from them. Endogenous variables also have paths leading into them. Recursive models have no paths with bidirectional flow. A saturated recursive model is one in which all possible recursive paths are present.

Examples A saturated recursive model. A nonsaturated recursive model.

Next time Path models