Calculate the sample standard deviation of the paired differences. Round your answer to six decimal places.

To test the effect of a physical fitness course on one's physical ability, the number of sit-ups that a person could do in one minute, both before and after the course, was recorded. Ten individuals are randomly selected to participate in the course. The results are displayed in the following table. Using this data, find the 99 % confidence interval for the true difference in the number of sit-ups each person can do before and after the course. Assume that the numbers of sit-ups are normally distributed for the population both before and after completing the course. Sit-ups after 56 | 38 | 46 | 51 | 48} 35 | 58] 31