A longitudinal study reported the scores shown below for four children on their age at first walking (in months) and their first-grade teachers' ratings of athletic ability (on a 9-point scale). (Note: TheZscores are figured for you.)

1. Compute the correlation coefficient.
2. Indicate possible directions of causality for the variables.

Age Walking

Athletic Rating

Child

Raw

Z

Raw

Z

A

12

-.13

5

.51

B

10

-1.17

4

-.08

C

10

-1.17

6

1.11

D

16

1.95

7

1.70