Table 2.
Expressions of the Mediation Measures by the Product Method and Difference Method Under the 4 Data Types of the Outcome and Mediator
| Data Type a |
b
|
b
|
b
|
Reference |
|---|---|---|---|---|
| Product method | ||||
Case 
|
|
|
|
(9, 14) |
Case 
|
|
|
|
(1, 14) |
Case  c
|
|
|
|
(14, 15) |
Case 
|
|
|
|
(14, 15) |
| Difference method | ||||
| All cases |
|
|
|
(2) |
Abbreviations: ARE, asymptotic relative efficiency; MP, mediation proportion; NDE, natural direct effect; NIE, natural indirect effect; TE, total effect.
a The mediation measures in cases 
and 
are defined on an identity scale. In cases 
and 
, the mediation measures are defined on a log risk ratio scale (also known as the log link function scale).
b
, 
, 
are the natural indirect effect, natural direct effect, and mediation proportion defined for the exposure in change from 
to a conditional on 
.
c In case 
, the product method additionally assume the error term in the mediator model 3 follows a homoscedastic normal distribution.