Psychological measures like the ones described are usually thought to represent interval data and thus produce score data. We are looking for a measure of relationship between these measures. Therefore, we would compute Pearson product-moment correlations. Since we have four measures (a, b, c, & d), we would have six different correlations (ab, ac, ad, bc, bd, & cd) that form a half-matrix as shown below.
a |
b |
c |
d |
|
a |
rab |
rac |
rad |
|
b |
rbc |
rbd |
||
c |
rcd |
|||
d |