Moderation & Mediation

Question 1

Grand mean centring

Answer 1

grand mean centring means the transformation of a variable by taking each score and subtracting the mean of all scores (for that variable) from it (cf. Group mean centring).

Question 2

Direct effect

Answer 2

the effect of a predictor variable on an outcome variable when a mediator is present in the model (cf. indirect effect).

Question 3

Index of mediation

Answer 3

a standardized measure of an indirect effect. In a mediation model, it is the indirect effect multiplied by the ratio of the standard deviation of the predictor variable to the standard deviation of the outcome variable.

Question 4

Indirect effect

Answer 4

the effect of a predictor variable on an outcome variable through a mediator (cf. direct effect).

Question 5

Interaction effect

Answer 5

the combined effect of two or more predictor variables on an outcome variable. It can be used to gauge moderation.

Question 6

Mediation

Answer 6

perfect mediation occurs when the relationship between a predictor variable and an outcome variable can be completely explained by their relationships with a third variable. For example, taking a dog to work reduces work stress. This relationship is mediated by positive mood if (1) having a dog at work increases positive mood; (2) positive mood reduces work stress; and (3) the relationship between having a dog at work and work stress is reduced to zero (or at least weakened) when positive mood is included in the model.

Question 7

Mediator

Answer 7

a variable that reduces the size and/or direction of the relationship between a predictor variable and an outcome variable (ideally to zero) and is associated statistically with both.

Question 8

Moderation

Answer 8

Moderation occurs when the relationship between two variables changes as a function of a third variable. For example, the relationship between watching horror films (predictor) and feeling scared at bedtime (outcome) might increase as a function of how vivid an imagination a person has (moderator).

Question 9

Moderator

Answer 9

a variable that changes the size and/or direction of the relationship between two other variables.

Question 10

Simple slopes analysis

Answer 10

an analysis that looks at the relationship (i.e., the simple regression) between a predictor variable and an outcome variable at low, mean and high levels of a third (moderator) variable.

Question 11

Sobel test

Answer 11

A significance test of mediation. It tests whether the relationship between a predictor variable and an outcome variable is significantly reduced when a mediator is included in the model. It tests the indirect effect of the predictor on the outcome