Updated 08/13/11 1
Mplus syntax files for single- and multilevel mediation models, to accompany:
Preacher, K. J., Zyphur, M. J., & Zhang, Z. (2010). A general multilevel SEM framework for
assessing multilevel mediation. Psychological Methods, 15, 209-233.
Preacher, K. J., Zhang, Z., & Zyphur, M. J. (2011). Alternative methods for assessing mediation
in multilevel data: The advantages of multilevel SEM. Structural Equation Modeling, 18, 161-
182.
Note: In models in which the Between and Within components of a 1→1 path are estimated
separately and the Within component is random, the Between component is estimated as the
contextual effect rather than as the Between slope in Mplus (see Mplus User's Guide, Ex.9.2). In
Examples F and J this has been addressed by adding the Within slope to the contextual effect to
yield the correct Between slope component before computing the indirect effect.
A. simple mediation
TITLE: simple mediation
DATA: FILE IS mydata.dat; ! text file containing raw data in long format
VARIABLE: NAMES ARE
x m y;
USEVARIABLES ARE
x m y;
ANALYSIS: BOOTSTRAP IS 5000; ! bootstrap is recommended for simple mediation
MODEL: ! model specification follows
m ON x; ! regress mediator on independent variable
y ON x m; ! regress outcome on both mediator and independent variable
MODEL INDIRECT: ! request significance test for indirect effect of x on y via m
y IND m x; ! indirect effect of interest (ending in y and starting with x)
OUTPUT: CINTERVAL(BCBOOTSTRAP); ! request bias-corrected bootstrap
! confidence intervals
B. 2-2-1 model with latent variables (MSEM)
TITLE: 2-2-1 mediation (similar code used in example 2)
DATA: FILE IS mydata.dat; ! text file containing raw data in long format
VARIABLE: NAMES ARE
group x1 x2 x3 m1 m2 m3 m4 m5 y1 y2 y3 y4 y5;
MISSING ARE *; ! missing data denoted "*" in mydata.dat
USEVARIABLES ARE
group x1 x2 x3 m1 m2 m3 m4 m5 y1 y2 y3 y4 y5;
BETWEEN ARE x1 x2 x3 m1 m2 m3 m4 m5; ! identify variables with only Between variance;
! variables that are not claimed as "BETWEEN ARE" or "WITHIN ARE" can have
! both Within and Between variance
CLUSTER IS group; ! Level-2 grouping identifier
ANALYSIS: TYPE IS TWOLEVEL RANDOM; ! tell Mplus to perform multilevel modeling
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