multilevel (version 2.7)

sobel: Estimate Sobel's (1982) Test for Mediation

Description

Estimate Sobel's (1982) indirect test for mediation. The function provides an estimate of the magnitude of the indirect effect, Sobel's first-order estimate of the standard error associated with the indirect effect, and the corresponding z-value. The estimates are based upon three models as detailed on page 84 of MacKinnon, Lockwood, Hoffman, West and Sheets (2002).

Usage

sobel(pred,med,out)

Arguments

pred

The predictor or independent variable (X).

med

The mediating variable (M).

out

The outcome or dependent variable (Y).

Value

Mod1: Y~X

A summary of coefficients from Model 1 of MacKinnon et al., (2002).

Mod2: Y~X+M

A summary of coefficients from Model 2 of MacKinnon et al., (2002).

Mod3: M~X

A summary of coefficients from Model 3 of MacKinnon et al., (2002).

Indirect.Effect

The estimate of the indirect mediating effect.

SE

Sobel's (1982) Standard Error estimate.

z.value

The estimated z-value.

N

The number of observations used in model estimation.

References

MacKinnon, D. P., Lockwood, C. M., Hoffman, J. M., West, S. G., Sheets, V. (2002). A comparison of methods to test mediation and other intervening variable effects. Psychological Methods, 7, 83-104.

Sobel, M. E., (1982). Asymptotic confidence intervals for indirect effects in structural equation models. In S. Leinhardt (Ed.), Sociological Methodology 1982 (pp. 290-312). Washington, DC: American Sociological Association.

Examples

# NOT RUN {
data(bh1996)

#A small but significant indirect effect indicates leadership mediates
#the relationship between work hours and well-being.
sobel(pred=bh1996$HRS,med=bh1996$LEAD,out=bh1996$WBEING)
# }