Path Analysis; Moderation
Mediator variable
- "In general, a given variable may be said to function as a mediator to the extent that it accounts for the relation between the predictor and the criterion. Mediators explain how external physical events take on internal psychological significance. Whereas moderator variables specify when certain effects will hold, mediators speak to how or why such effects occur.
2 step move to a moderation
1- IV's are centered unless categorical Note: Centering is where you recalculate the IV scores by subtracting the mean (a constant) from each score (0= score on mean, - below, + above) 2-DV regresses onto centered IV's, and the interactive product of the variables (product is created by using a compute statement) -Hierachical analysis: the key test is whether the interaction term explains significant variance over and above the two main effects -Assessed by beta weight of the interaction term
Example of Moderation
1- mind readings tasks 2-Given accuracy scores found women happier in relationships more accurate mind readers, but not so for men SO, authors moderated link between relationship sat and mind reading accuracy through relationship length
Moderation analyses
>Done using hierarchical multiple regression (when one or more IV are continuous) >This analysis is equivalent to testing interactions using ANOVA (when two IV's are categorical) -DIFFERENT to mediation designs (IV's can be mixture of categorical and continuous) -IV's effect on the DV may be MODERATED by the MV
Moderator variable
>Moderator variables - "In general terms, a moderator is a qualitative (e.g., sex, race, class) or quantitative (e.g., level of reward) variable that affects the direction and/or strength of the relation between an independent or predictor variable and a dependent or criterion variable. >Specifically within a correlational analysis framework, a moderator is a third variable that affects the zero-order correlation between two other variables. ... In the more familiar analysis of variance (ANOVA) terms, a basic moderator effect can be represented as an interaction between a focal independent variable and a factor that specifies the appropriate conditions for its operati
Actual calculation of a path analysis moderation
>usually just use a website >Based on overall regression equation -Y = Bx1 + Bx2 + Bx1X2 (X1 * X2) + c We need to draw a graph with -The Y axis on the left (mind-reading accuracy) -Relationship satisfaction on the bottom (high versus low), -Relationship length as the moderating variable (high versus low) >We place four hypothetical men on a graph (and assign scores +/- one SD)
Why moderation
A moderation model can help to answer the question "do differing levels of the moderator variable (ModV) change the relationship between my independent variable (IV) and my dependent variable (DV)?". A mediating variable helps to explain the mechanism by which an IV causes a DV (think of it like how much of the variance in the relationship between the IV and the DV is explained by the mediating variable), whereas a moderator variable dictates the strength of a relationship between the IV and the DV. Moderator variables are usually stable variables such as personality traits or gender - things that don't tend to change over time. A couple of examples will help in understanding this:
Hierarchical analysis
Hierarchical task analysis (HTA) is a task description method and a variant of task analysis. Task description is a necessary precursor for other analysis techniques, including critical path analysis (CPA). HTA is used to produce an exhaustive description of tasks in a hierarchical structure of goals, sub-goals, operations and plans.[9] In HTA, tasks are broken down into progressively smaller units
Interaction
Interactions are when the effect of two, or more, variables is not simply additive. This page describes the interaction between two variables.
Breaking down results moderation
To interpret these results, break it down by the levels of the moderator variable (relationship length): For males in a short relationship, with low relationship satisfaction, mind-reading accuracy was higher/lower (delete one) compared to the males in a short relationship with high relationship satisfaction. For males in a long relationship, with low relationship satisfaction, mind-reading accuracy was higher/lower (delete one) compared to the males in a long relationship with high relationship satisfaction. Is this result consistent with our hypothesis?
