What Does Squaring Pearson's R Give Us

Multiple Choice

What does squaring Pearson's r give us?

A) the change in Y associated with a one unit change in X
B) the proportional reduction in error for predicting Y when we have knowledge of X
C) a clear index of relationship strength based on whether r² is between 0 and 0.1, 0.1 and 0.3, or over 0.3
D) a clear index of relationship strength based on whether r² is less than or greater than 0.5