You are trying to predict how long a relationship will last (TIME) based on scores of social compatibility (COMP; how much they like doing the same things, have the same hobbies etc) and how physically attracted the person feels towards the other (ATTRACT). You obtain the following simple correlations.
TIME COMP
ATTRACT .43 .67
COMP .56 1.00
a) How much of the variance in length of relationship can be explained by compatibility and attraction?
b) How much of an improvement in prediction is gained by using both predictors over just compatibility?
c) What would the multiple correlation be?