9.67.* The formula for the correlation can be expressed as

(a) Using the first formula, explain why the correlation has the same value when x predicts y as when y predicts x.

(b) By the second formula, the correlation is approximately the average product of the z-score for x times the z-score for y. Use this to explain why the correlation does not depend on the units of measurement. (Note: For the population, page 92 showed an analogous formula.)

Transcribed Image Text:

r = (x-x)(y-y) 1 +(=)) (?). n