Product moment correlation: what degree of relation is present, the statistic is denoted as rxy, and is calculated over n pairs of observations, with a perfect correlation, all points in the scattergram fall on a straight line. A pos z-score means you"re above the mean, a z-score of 1 = right on the mean: if you scored above the mean on both, multiply them, you"ll still be above the mean positive correlation. A neg z-score means you"re below the mean: if you scored below the mean on both, multiply them, the product is positive positive correlation. If you got above on one and below on the other, multiply them, the product is negative negative correlation. Every score minus the mean times the standard deviation. True score: the average of all the measured scores (observed scores) Note: the measurements vary considerably, measurements close to 1. 2 cm occur more frequently than measurements at either exreme.