The average number of days to complete recovery from a particular type of knee operation is 123.7 days. From his experience, a physician suspects that use of a topical pain medication might be lengthening the recovery time. He randomly selects the records of seven knee surgery patients who used the topical medication. The times to total recovery were: 128 135 121 142 126 151 123 a) Find the 95% confidence interval for the population mean. b) Test physician's claim at a = 0.05. .