Mediation Regression Analysis Flashcards
What is a mediator?
A variable that explains a portion of the association between Y and X1
What is mediation?
A hypothesised causal mechanism by which one variable affects another
In a mediation model, what is c’?
The direct effect of X1 on Y
In a mediation model, how do you calculate the indirect (mediated) effect?
A x B
(effect of X1 in M times effect of M on Y)
What is the total effect (C)?
Direct + indirect effect
c’ + (axb)
What are Baron and Kenny’s four steps for determining mediation?
- Test path c (X1 –> Y)
- Test path a (X1 –> M)
- Test path b (M –> Y, controlling for X1)
- Test path c’ (X1 –> Y, controlling for M)
If β3 (path c’) from the multiple linear regression is approaching zero (p>0.05), what can you conclude?
Complete mediation - there’s no effect of X1 on Y when controlling for M
The mediator substantially reduces the effect of X1 on Y
If β3 (path c’) from the multiple linear regression is significantly different from zero (p<0.05), what can you conclude?
Partial mediation - there is still an effect of X1 on Y when controlling for M
If there is partial mediation, c’ will be _____________ than c
Smaller
Which is Baron and Kenny’s steps are essential for establishing mediation?
Steps 2 and 3 - estimates indirect effect
What do newer methods recommend testing to establish mediation?
Only the indirect effect (paths a and b)
What is the Sobel test?
▪️Normal theory approach to testing indirect effect
▪️H0: a x b = 0
▪️Based on approximate z-statistic
When do you reject the null hypothesis of the Sobel test?
If Z in absolute value is greater than 1.96
When does the Sobel test work best and why?
In large samples because skewness is reduced
What are the limitation of the Sobel test?
▪️Based on normal approximation but sampling distribution of ab is highly skewed
▪️Large values much more variable
▪️Lowers statistical power
