Refer to Exercise 6.13. A second study was done the following year. A treatment group of 1...

Refer to Exercise 6.13. A second study was done the following year. A treatment group of 18 plumbers was assigned a dispatcher who monitored all the plumbers' incoming requests for service and outlined a service strategy for that day's activities. A control group of 18 plumbers was to conduct their activities as they did in the past, by providing service in roughly sequential order for s tacks of service calls received. The average daily mileages for these 36 plumbers were computed over a 30-day period and are recorded here.

a. The sample data are plotted next. Based on these plots, which procedure appears more appropriate for comparing the distributions of the two groups?

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b. Computer output is shown here for a t test and a Wilcoxon rank sum test. (which is equivalent to the Mann-Whitney test shown in the output). Compare the results foor these two tests and draw a conclusion about the effectiveness of the dispatcher program.

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c. Comment on the appropriateness or inappropriateness of the t test based on the plots of the data and the computer output.

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d. Does it matter which test is used here? Might it be reasonable to run both tests in certain situations? Why or why not?

Exercise 6.13

A plumbing contractor was interested in making her operation more efficient by cutting down on the average distance between service calls while still maintaining at least the same level of business activity. One plumber (p lumber 1) was assigned a dispatcher who monitored all his incoming requests for service and outlined a service strategy for that day. Plumber 2 was to continue as she had in the past, by providing service in roughly sequential order for stacks of service calls received. The total daily mileages for these two plumbers are recorded here for a total of 18 days (3 workweeks).