mod: Moderation

In medmod: Simple Mediation and Moderation Analysis

Moderation

Description

Simple moderation analysis. Estimates a model in which the effect of a predictor on the dependent variable depends on the value of a moderator, testing the main effects of predictor and moderator and their interaction. All variables are mean-centered before the model is fitted with the lavaan package (Rosseel, 2012); standard errors are computed with the delta method or by bootstrapping. Optionally provides a simple slope analysis with a corresponding plot, and an annotated path diagram of the model.

Usage

mod(
  data,
  dep,
  mod,
  pred,
  estMethod = "standard",
  bootstrap = 1000,
  label = FALSE,
  test = TRUE,
  ci = FALSE,
  ciWidth = 95,
  pathDiagram = FALSE,
  pathDiagramLabel = TRUE,
  pathDiagramEst = TRUE,
  pathDiagramSig = TRUE,
  pathDiagramMainEffect = FALSE,
  simpleSlopeEst = FALSE,
  simpleSlopePlot = FALSE
)

Arguments

data	the data as a data frame
dep	a string naming the dependent variable
mod	a string naming the moderator 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
label	TRUE or FALSE (default), provide the coefficient labels (b1, b2, b3) used in the model and the path diagram
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'
pathDiagram	TRUE or FALSE (default), provide a conceptual path diagram of the moderation 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.
pathDiagramMainEffect	TRUE or FALSE (default), draw the moderator's main effect on the dependent variable (b2) in the path diagram.
simpleSlopeEst	TRUE or FALSE (default), provide the estimates of the simple slopes.
simpleSlopePlot	TRUE or FALSE (default), provide a plot of the simple slopes.

Value

A results object containing:

results$mod					a table containing moderation estimates
results$pathDiagram					an image
results$simpleSlope$estimates					a table containing the simple slope estimates
results$simpleSlope$plot					an image
results$modelSyntax					the lavaan syntax used to fit the moderation model

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

results$mod$asDF

as.data.frame(results$mod)

Examples

set.seed(1234)
X <- rnorm(100)
M <- rnorm(100)
X_M <- X*M
Y <- 0.7*X + 0.1*M + 4.2*X_M + rnorm(100)
dat <- data.frame(X=X, M=M, Y=Y)

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

#
#  Moderation Estimates
#  --------------------------------------------------
#             Estimate    SE        Z        p
#  --------------------------------------------------
#    X           0.951    0.0965     9.86    < .001
#    M          -0.471    0.0923    -5.10    < .001
#    X:M         4.185    0.1009    41.50    < .001
#  --------------------------------------------------
#
#

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