med: Mediation
In medmod: Simple Mediation and Moderation Analysis

med	R Documentation

Mediation

Description

Simple mediation analysis. Estimates the indirect, direct and total effects of a model in which a predictor influences the dependent variable through a mediator. The model is fitted with the lavaan package (Rosseel, 2012); standard errors are computed with the delta method (equivalent to the Sobel test for the indirect effect) or by bootstrapping. Optionally provides the individual path estimates, an estimate plot, and an annotated path diagram of the model.

Usage

med(
  data,
  dep,
  med,
  pred,
  estMethod = "standard",
  bootstrap = 1000,
  test = TRUE,
  ci = FALSE,
  ciWidth = 95,
  pm = FALSE,
  paths = FALSE,
  label = FALSE,
  estPlot = FALSE,
  pathDiagram = FALSE,
  pathDiagramLabel = TRUE,
  pathDiagramEst = TRUE,
  pathDiagramSig = TRUE
)

Arguments

`data`	the data as a data frame
`dep`	a string naming the dependent variable
`med`	a string naming the mediator variable
`pred`	a string naming the predictor variable
`estMethod`	`'standard'` (default), or `'bootstrap'`, the estimation method to use
`bootstrap`	a number between 1 and 100000 (default: 1000) specifying the number of samples that need to been drawn in the bootstrap method
`test`	`TRUE` (default) or `FALSE`, provide 'Z' and 'p' values for the mediation estimates
`ci`	`TRUE` or `FALSE` (default), provide a confidence interval for the mediation estimates
`ciWidth`	a number between 50 and 99.9 (default: 95) specifying the confidence interval width that is used as `'ci'`
`pm`	`TRUE` or `FALSE` (default), provide the percent mediation effect size for the mediation estimates
`paths`	`TRUE` or `FALSE` (default), provide the individual estimates of the paths in the mediation model
`label`	`TRUE` (default) or `FALSE`, provide insightful labels for all estimates
`estPlot`	`TRUE` or `FALSE` (default), provide an estimate plot where for each estimator the estimated coefficient and confidence intervals are plotted.
`pathDiagram`	`TRUE` or `FALSE` (default), provide a path diagram of the mediation model.
`pathDiagramLabel`	`TRUE` (default) or `FALSE`, annotate the path diagram arrows with the path labels.
`pathDiagramEst`	`TRUE` (default) or `FALSE`, annotate the path diagram arrows with the estimated coefficients.
`pathDiagramSig`	`TRUE` (default) or `FALSE`, annotate the path diagram arrows with significance stars.

Value

A results object containing:

`results$med`					a table containing mediation estimates
`results$paths`					a table containing the individual path estimates
`results$pathDiagram`					an image
`results$estPlot`					an image
`results$modelSyntax`					the lavaan syntax used to fit the mediation model

Tables can be converted to data frames with asDF or as.data.frame. For example:

results$med$asDF

as.data.frame(results$med)

Examples

set.seed(1234)
X <- rnorm(100)
M <- 0.5*X + rnorm(100)
Y <- 0.7*M + rnorm(100)
dat <- data.frame(X=X, M=M, Y=Y)

med(dat, dep = "Y", pred = "X", med = "M")

#
#  Mediation Estimates
#  -----------------------------------------------------
#    Effect      Estimate    SE        Z        p
#  -----------------------------------------------------
#    Indirect      0.3736    0.0920    4.059    < .001
#    Direct        0.0364    0.1044    0.348     0.728
#    Total         0.4100    0.1247    3.287     0.001
#  -----------------------------------------------------
#
#

medmod documentation built on July 16, 2026, 9:07 a.m.