SocGrades: Grades in a Sociology Course
In heplots: Visualizing Hypothesis Tests in Multivariate Linear Models

Description Usage Format Details Source Examples

The data set SocGrades contains four outcome measures on student performance in an introductory sociology course together with six potential predictors. These data were used by Marascuilo and Levin (1983) for an example of canonical correlation analysis, but are also suitable as examples of multivariate multiple regression, MANOVA, MANCOVA and step-down analysis in multivariate linear models.

1	data(SocGrades)

A data frame with 40 observations on the following 10 variables.

class: Social class, an ordered factor with levels 1 > 2 > 3
sex: sex, a factor with levels F M
gpa: grade point average
boards: College Board test scores
hssoc: previous high school unit in sociology, a factor with 2 no, yes
pretest: score on course pretest
midterm1: score on first midterm exam
midterm2: score on second midterm exam
final: score on final exam
eval: course evaluation

midterm1, midterm2, final, and possibly eval are the response variables. All other variables are potential predictors.

The factors class, sex, and hssoc can be used with as.numeric in correlational analyses.

Marascuilo, L. A. and Levin, J. R. (1983). Multivariate Statistics in the Social Sciences Monterey, CA: Brooks/Cole, Table 5-1, p. 192.

data(SocGrades)
# basic MLM
grades.mod <- lm(cbind(midterm1, midterm2, final, eval) ~ 
	class + sex + gpa + boards + hssoc + pretest, data=SocGrades)
	
Anova(grades.mod, test="Roy")

clr <- c("red", "blue", "darkgreen", "magenta", "brown", "black", "darkgray")
heplot(grades.mod, col=clr)
pairs(grades.mod, col=clr)

## Not run: 
heplot3d(grades.mod, col=clr, wire=FALSE)

## End(Not run)

if (require(candisc)) {
	# calculate canonical results for all terms
	grades.can <- candiscList(grades.mod)
	# extract canonical R^2s
	unlist(lapply(grades.can, function(x) x$canrsq))
	# plot class effect in canonical space
	heplot(grades.can, term="class", scale=4)	

	# 1 df terms: show canonical scores and weights for responses
	plot(grades.can, term="sex")
	plot(grades.can, term="gpa")
	plot(grades.can, term="boards")
	}