Estimate Sobel's (1982) indirect test for mediation. The function provides an estimate of the magnitude of the indirect effect, Sobel's firstorder estimate of the standard error associated with the indirect effect, and the corresponding zvalue. The estimates are based upon three models as detailed on page 84 of MacKinnon, Lockwood, Hoffman, West and Sheets (2002).
1  sobel(pred,med,out)

pred 
The predictor or independent variable (X). 
med 
The mediating variable (M). 
out 
The outcome or dependent variable (Y). 
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 zvalue. 
N 
The number of observations used in model estimation. 
Paul Bliese paul.bliese@moore.sc.edu
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, 83104.
Sobel, M. E., (1982). Asymptotic confidence intervals for indirect effects in structural equation models. In S. Leinhardt (Ed.), Sociological Methodology 1982 (pp. 290312). Washington, DC: American Sociological Association.
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