In Order to Compute a Correlation Coefficient Between Traits a and B

Multiple Choice

In order to compute a correlation coefficient between traits A and B, it is necessary to have:

A) one group of subjects, some of whom possess characteristics of trait A, the remainder possessing those of trait B.
B) measures of trait A on one group of subjects and of trait B on another.
C) one group of subjects, some of whom have both A and B, some have neither, and some have one but not the other.
D) two groups of subjects, one which could be classified as A or not A, the other as B or not B.
E) measure of traits A and B on each subject in one group.