VocabGrowth {heplots} | R Documentation |
Data from the Laboratory School of the University of Chicago. They consist of scores from a cohort of pupils in grades 8-11 on the vocabulary section of the Cooperative Reading Test. The scores are scaled to a common, but arbitrary origin and unit of measurement, so as to be comparable over the four grades.
data(VocabGrowth)
A data frame with 64 observations on the following 4 variables.
grade8
grade9
grade10
grade11
Since these data cover an age range in which physical growth is beginning to decelerate, it is of interest whether a similar effect occurs in the acquisition of new vocabulary.
R.D. Bock, Multivariate statistical methods in behavioral research, McGraw-Hill, New York, 1975, pp453.
Keesling, J.W., Bock, R.D. et al, "The Laboratory School study of vocabulary growth", University of Chicago, 1975.
data(VocabGrowth) # Standard Multivariate & Univariate repeated measures analysis Vocab.mod <- lm(cbind(grade8,grade9,grade10,grade11) ~ 1, data=VocabGrowth) idata <-data.frame(grade=ordered(8:11)) Anova(Vocab.mod, idata=idata, idesign=~grade) # calculate Y M, using polynomial contrasts trends <- as.matrix(VocabGrowth) %*% poly(8:11, degree=3) colnames(trends)<- c("Linear", "Quad", "Cubic") # test all trend means = 0 == Grade effect within.mod <- lm(trends ~ 1) Manova(within.mod) heplot(within.mod, terms="(Intercept)", col=c("red", "blue"), type="3", term.labels="Grade", main="HE plot for Grade effect") points(0,0, cex=2.5, col="green", pch=19) text(0,0, expression(H[0]), col="green", pos=2) abline(h=0, col="green") abline(v=0, col="green")