Two different arthroscopic surgery techniques have been developed for correcting serious knee injuries. (Call the surgical techniques Technique A and Technique B.) You are interested in assessing the difference in average healing times for the two procedures. You select 50 patients to undergo surgical Technique A, and 50 patients to undergo surgical Technique B. Average recovery time for Technique A patients turns out to be 95 days, with standard deviation of 12 days. For Technique B patients, average recovery time is 88 days, with standard deviation of 8 days. Treating the two patient groups as simple random samples, construct the 95% confidence interval estimate of the difference in average recovery times for the population of all Technique A patients and the population of all Technique B patients.