Moderation & Mediation Flashcards
What is moderation?
Moderation occurs when the relationship between two variables depends on a third variable.
When the two predictors interact leading to a mechanism being created.
Above the main effects.
What is needed for moderation?
Outcome must be continuous + normally distributed.
Continuous predictor + centred.
Why do we centre predictors?
Usually the interaction effect is interpreted when all other predictors are 0.
0 is often not sensible (sometimes not even defined in the scale!).
Centring - people with average value in both predictors.
How many effects will there be in moderation?
3. Main effect of X. Main effect of M. Interaction effect. (Basically like a multiple regression with three predictors).
What other program do you have to use for a moderation?
PROCESS.
How do you run assumption checks?
You can’t in PROCESS!
Give 3 advantages of PROCESS?
Centring automated, syntax to plot simple slopes, Johnson-Neyman method.
Explain the Johnson-Neyman method.
Need to look at the column of p-values and find where it becomes non-significant (if it changes!).
How do you compute a simple slope plot?
Need to copy the syntax into SPSS.
What is the definition of mediation?
The relationship between predictor and outcome variable can be partially explained by their relationship with a third variable.
Predictor influences the mediator, the mediator influences the outcome variable.
Indirect effect between X and Y. Mediated by M.
What is needed for mediation?
Outcome variables must be continuous.
Must use bootstrap method.
What is a, b, c’, a*b?
a - X-M. b - M-Y. c' - X-Y. a*b - X-M-Y. (indirect). c = c' + a*b.
What is the bootstrap method?
Allows us to create new datasets based on the one dataset we have.
Non-parametric method.
Why do we use bootstrap (mediation)?
To calculate standard errors properly (otherwise we can’t know if the indirect effect is normally distributed).
What model number do we use for mediation?
4.
Number of bootstrap samples - 5000.
