A commuter train is scheduled to arrive at a particular station at 8 : 05 a.m. Regulations state that the standard deviation of the difference between the actual arrival time and 8: 05 a.m. should be no more than 4 minutes. To determine if this requirement is being met, the arrival times on each of 24 randomly selected days were observed, and the difference, in minutes, between the arrival time and 8 : 05 a.m. was recorded. A negative value for this difference means that the train arrived early. The data collected are summarized in the following histogram: Frequency 6 5- 3 -8 -4 0 8 Difference in arrival time (in minutes) Based on this histogram, estimate the standard deviation of the sample of 24 time differences. Carry your intermediate computations to at least four decimal places, and round your answer to at least one decimal place. (If necessary, consult a list of formulas.) X