Moderated Simple Slopes

Description

Computes the simple slopes for a moderated regression model.

Usage

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sim.slopes(mod, z, zsd = 1, mcz = FALSE)

Arguments

mod

linear model - usually constructed with moderate.lm

z

moderating variable

zsd

Multiple for SD of z; number of SDs from mean to construct simple slopes

mcz

logical whether z is already centered or not in the original data

Details

Constructs the simple slopes for arbitrary values of z (e.g., +/- 1, 2, 3 standard deviations) involved in a moderated multiple regression equation.

Value

A table with the following values for zHigh (Meanz + zsd*SDz), Mean(Meanz), and zLow (Meanz - zsd*SDz):

INT

Intercept of simple slope

Slope

Slope of the simple slope

SE

Standard Error of the slope

LCL, UCL

Lower and Upper confidence limits for slope

Author(s)

Thomas D. Fletcher tom.fletcher.mp7e@statefarm.com

References

Aiken, L. S., & West, S. G. (1991). Multiple regression: Testing and interpreting interactions. Newbury Park: Sage Publications.

Cohen, J., Cohen, P., West, S. G., & Aiken, L. S. (2003). Applied multiple regression/correlation analysis for the behavioral sciences, 3rd ed. Mahwah, NJ: Lawrence Erlbaum Associates.

See Also

moderate.lm, graph.mod

Examples

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data(tra)
lm.mod1 <- moderate.lm(beliefs, values, attitudes, tra)
ss.mod1 <- sim.slopes(lm.mod1, tra$values)
ss.mod1