A nurse is interested in whether there is a relationship between daily levels of stress and likelihood of a heart attack. The stress scores (predictor variable) and risk of heart attack values (criterion variable) from a small sample of participants are depicted below (Values below are valid for this question only!) Stress Score Risk of Heart Attack (Higher values = more stress) (Higher values = greater risk) 8 0 5 1 4 9 5 5 What is the covariance?