Suppose that we are interested in the relationship between the age of the individuals who are members of our managed-care organization and the use of physician care, as measured by visits. Suppose also that after selecting 15 members at random we obtained the following paired observations:
Visits: 3 5 4 2 1 3 6 7 4 5 10 1 2 3 8
Age 28 45 50 19 16 27 54 63 32 42 68 19 23 30 61
Use these data to find the covariance between age and the number of visits.