A drug is suspected of causing an elevated heart rate in a certain group of high-risk patients. Twenty patients from the group were given the drug. The changes in heart rates were found to be as follows.
-1 8 5 10 2 12 7 9 1 3
4 6 4 12 11 2 -1 10 2 8
Construct a 98% con?dence interval for the mean change in heart rate. Assume that the population has a normal distribution. Interpret your answer.