The following correlation matrix is given by Allison and Ciechetti (1976) in a study of sleep in mammals:
where the random variables are defined as
Y1 = Stow-wave sleep
Y2 = Paradoxical sleep
Y3 = Life span
Y4 = Body weight
Y5 = Brain weight
Y6= Gestation time
Y7= Predation index
Y8= Sleep exposure
Y9= Overall danger
Carry out a cluster analysis of the variables by means of (a) the varimax rotation Eq. (5.20) and (b) the oblimin in criterion (Eq. 5.28) by using the first r = 2 principal components. Which rotation results in a clearer identification of the component axes?
