In an effort to provide more consistent customer service, the manager of a local fast-food restaurant would like to know the dispersion of customer service times about their average - value for the facility’s drive-up window. The file P2_4.XLS contains 200 customer service times, all of which were observed during the busiest hour of the day for this fast-food operation.

a. Find and interpret the variance and standard deviation of these sample values.

b. Are the rules of thumb applicable in this case? If so, apply the rules of thumb and interpret your results. If not, explain why the rules of thumb are not applicable here.