You are interested in if stress levels and exercise are correlated with resting heart rate. You ask participants to rank their stress on a scale from 1-10, how many hours of exercise they do a week, and take their resting heart rate as beats per minute. You run some R code and get the following correlations:

r_{stress,heart rate} = 0.53

r_{exercise,heart rate} = -0.15

You run a partial correlation for the relationship between stress and heart rate controlling for exercise using the function pcor(). Your partial correlation is r_{stress,heart rate} = 0.50.

How much explanatory power did stress lose when controlling for exercise? (Hint: Chapter 7 section How to understand R Output for Partial Correlation may be helpful)

3%

38%

9%

25%

Cannot be calculated