A clinical psychologist has observed that there appears to be an association between parental anger and childhood self-esteem. In particular, parents who score higher on ratings of anger and hostility tend to have children who have lower self-esteem. If this psychologist's impressions are correct, the relation between parental anger and childhood self-esteem would be an example of a
a. positive correlation
b. causal correlation
c. negative correlation
d. random correlation