ZYmediate: Robust mediation test

In WRS2: A Collection of Robust Statistical Methods

Robust mediation test

Description

Performs a robust mediation test according to the method proposed by Zu & Yuan (2010).

Usage

ZYmediate(x, y, med, nboot = 2000, alpha = 0.05, kappa = 0.05, ...)

Arguments

x	vector with predictor values.
y	vector with response values.
med	vector with mediator values.
nboot	number of bootstrap samples.
alpha	alpha level.
kappa	the percent of cases to be controlled when robust method is used.
...	currently ignored.

Value

ZYmediate returns an object of class "robmed" containing:

a.est	effect of predictor on mediator)
b.est	effect of mediator on response (in multiple regression model which includes the predictor as well)
ab.est	indirect effect (mediation effect)
CI.ab	confidence interval mediation effect
p.value	p-value mediation test
call	function call

References

Zu J., Yuan, K.-H. (2010). Local influence and robust procedures for mediation analysis. Multivariate Behavioral Research, 45, 1-44.

Examples

## Leerkes data:
## Y: Efficacy
## X: MatCare
## M: Esteem

## fitting robust mediator regressions
require(MASS)
summary(rlm(Efficacy ~ MatCare, data = Leerkes))
summary(rlm(Esteem ~ MatCare, data = Leerkes))
summary(rlm(Efficacy ~ MatCare + Esteem, data = Leerkes))

## robust testing of mediating effect (indirect effect)
with(Leerkes, ZYmediate(MatCare, Efficacy, Esteem))

WRS2 documentation built on March 19, 2024, 3:08 a.m.