In a study of heart surgery, one issue was the effect of drugs called beta-blockers on the pulse rate of patients during surgery. Thirty six patients were selected to receive beta-blockers before heart surgery and each was matched to a control patient based on prior medical history and measured pulse rates (control patients received a placebo prior to surgery). The pulse rate of each patient at a critical point during the operation was recorded. The mean difference in pulse rates between treatment and matched control patients was -3.1 (in other words, the mean across all matched pairs of the treatment case pulse rate minus the matched control case pulse rate was found to be -3.1, indicating pulse rates were lower on average in the treatment group). The standard deviation of those differences was 8.0. Do beta-blockers reduce the pulse rate? Use = .01.