The operations manager of a toll booth, located at a major exit of a state turnpike, is trying to estimate the variability of the number of vehicles that arrive at the toll booth during a 1-minute period during the peak of rush-hour traffic. In an effort to estimate this measure of dispersion, he records the number of vehicles that arrive.at the toll booth over a 1-minute interval commencing at the same time for each of 365 normal weekdays. These data are contained in the file P2_9.XLS. 

a. Is the sample variance (or sample standard deviation) a reliable measure of dispersion in this case? Explain why or why not. 

b. If the sample variance (or sample standard deviation) is not a reliable measure of dispersion in this case, how can this operations manager most appropriately measure the variability of the values in the given sample?