Simple slopes analysis for Moderated regression

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Description

Simple slope analysis according to Cohen, Cohen, West, & Aiken (2003); Bauer & Curran, (2005); and Dawson and Richter (2006) approaches.

Usage

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simpleSlope(object, pred, mod1, mod2, coded, ...)
## Default S3 method:
simpleSlope(object, pred, mod1, mod2="none",coded = "none", ...)

Arguments

object

an object of class "lmres": a moderated regression function.

pred

name of the predictor variable

mod1

name of the first moderator variable

mod2

name of the second moderator variable. Default "none" is used in order to analyzing two way interaction,

coded

a character vector of coded variables

...

Details

Simple slope analysis for moderated regression. If two way interaction is analyzed, the function computes simple slope analysis and region of significance( Bauer & Curran, 2005). If three way interaction is analyzed, the function compute simple slope analysis and difference slope test (Dawson and Richter, 2006).

Value

simpleSlope returns an object of class "simpleSlope".

An object of class "simpleSlope" is a list containing at least the following components:

nomY

the name of dependent variable

orde

it's 2 for two way interaction, it's 3 for three way interaction

points

Estimated points of dependent variable as a function of levels of moderators and predictor

simple_slope

a matrix summarizing simple slopes results

delta_slope

(only for three way interaction)a matrix summarizing difference slope tests

Df

degree of freedom

conf95

(only for two way interaction)confidence interval of moderator region of significance

Author(s)

Alberto Mirisola and Luciano Seta

References

-Bauer, D. J., & Curran, P. J. (2005). Probing Interactions in Fixed and Multilevel Regression: Inferential and Graphical Techniques. Multivariate Behavioral Research, 40(3), 373-400. -Cohen, J., Cohen, P.,West, S. G.,& Aiken, L. S. (2003). Applied multiple regression/correlation analyses for the behavioral sciences (3rd ed.). Mahwah, NJ: Lawerence Erlbaum Associates, Inc. - Dawson, J. F., and Richter, W. (2006) Probing Three-Way interactions in moderated multiple regression: Development and application of a slope difference test. Journal of Applied Psychology, 4, 917-926.

See Also

“summary.simpleSlope”

Examples

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	## simple slope for three way interaction
	
	library(car)
	data(Highway1)
	model3<-lmres(rate~len*trks*sigs1, centered=c("len","trks","sigs1"),data=Highway1)
    S_slopes<-simpleSlope(model3,pred="len",mod1="trks", mod2="sigs1")


## The function is currently defined as
function (object, pred, mod1, mod2, coded, ...) 
UseMethod("simpleSlope")