A medical researcher wanted to compare two different methods, A and B, for measuring cardiac output. Method A is the "gold standard" but invasive (involves inserting a catheter into the main heart artery). Method B is less accurate, but noninvasive. The researcher wanted to find out if there is a difference in the measurements obtained by the two methods. Data are measured on 15 patients, where each patient is measured using both methods. Data are recorded below.