Question

The Tri-City Office Equipment Corporation sells an imported copier on a franchise basis andperforms preventive maintenance and repair service on this copier. The data below have beencollected from 45 recent calls on users to perform routine preventive maintenance service; foreach call, X is the number of copiers serviced and Y is the total number of minutes spent bythe service person. Assume that first-order regression model (1.1) is appropriate CH01PR20.txt (a) Estimate the change in the mean service time when the number of copiers serviced increases by one. Use a 90 percent confidence interval. Interpret your confidence interval. (d) The manufacturer has suggested that the mean required time should not increase by more than 14 minutes for each additional copier that is serviced on a service call. Conduct a test to decide whether this standard is being satisfied by Tri-City. Control the risk of a Type I error at 0.05. State the alternatives, decision rule, and conclusion. What is the P-value of the test? (e) Does b subscript 0 give any relevant information here about the ``start-up" time on calls, that is, about the time required before service work is begun on the copiers at a customer location?

20 2
60 4
46 3
41 2
12 1
137 10
68 5
89 5
4 1
32 2
144 9
156 10
93 6
36 3
72 4
100 8
105 7
131 8
127 10
57 4
66 5
101 7
109 7
74 5
134 9
112 7
18 2
73 5
111 7
96 6
123 8
90 5
20 2
28 2
3 1
57 4
86 5
132 9
112 7
27 1
131 9
34 2
27 2
61 4
77 5

Answer 1

Here I've used R software to give an answer this question.

Code:

OUTPUT

(a) The estimated change in the mean service time when the number of copiers serviced increases by one = 15.0352

The 90% confidence interval is (14.22314, 15.84735)

There is a 90% chance that the estimated mean value of the variable X likely to fall in that interval.

(d)

Decision rule: We reject the null hypothesis at level 0.05 if p-value < 0.05.

Conclusion: Here the p-value = 0.1558 > 0.05, so we conclude on the basis of the given data that this standard is being satisfied by Tri-City.