Please explain! ST 260 Sample Questions Test3 Case 1 -Copier Maintenance. A cert
ID: 3369318 • Letter: P
Question
Please explain!
ST 260 Sample Questions Test3 Case 1 -Copier Maintenance. A certain company sells and repairs copiers under contract, and many of their clients have multiple machines. A part of the agreement calls for the company to perform regular maintenance on the machines at each location. The company is interested in estimating (predicting) the amount of Time (at the customer's place of business) that these regular service calls will require, based on the number of machines that need to be single employee is dispatched. (See output below.) Serviced. For any service al a Please see some output on separate sheet in answering the following questions. Wht is thpedicted service Time required on a service call for a client that has that has five copiers? (A) 74.6 (B) 77.2 (C) 71.8 What is the coefficient of correlation (rm) between Service and Time? (A) 0.916 2.-- (B) 0.934 (C) 0957 (D) 0.978 One of the data points is marked on the scatterplot by an X. The (X, Y) coordinates for this point are (8, 100). What is the residual or error value associated with this data point (A) -19.7 (B) 14.8 (C) -16.3 (D) 18.4 Using the model developed here, the predicted service Time required on a service call for a client that has 18 copiers is approximately 270 minutes. Which of the following statements describes a valid concern for such an estimate? 4.-- The model assumes that a single service employce is dispatched, but a job of this size (A) (B) It is improper to apply this estimated regression equation to values that are so far outside (C) This would introduce a large leverage value that might significantly impact the regression (D) The error or residual value for such a large number of copiers would make the estimate would likely require more than one, making the prediction invalid. the range of the sample data. results. unreliable ) The error or residual value for such a large number of copiers would make the estimate 5.What value is the measure of total variability in Time spent on service calls? (D) 76960 (A) 80377 (B) 3416 (C) 969 What proportion of this total variability is explained or accounted for by the number of copiers Serviced? (A) 0.916 (B) 0.934 (C) 0.957 (D) 0.978Explanation / Answer
We have given the regression output.
From the output we have to answer questions.
1) The regression equation is,
y = -0.580157 + 15.0352*x
Now we have to predict y when x = 5
y = -0.580157 + 15.0352*5 = 74.60
Option A) is correct.
2) COefficient of correlation between service and time.
Rsq = R sqaure = 95.7% = 0.957
Correlation coefficient = sqrt(0.957) = 0.9783
Option d) is correct.
5) Total variability in time spent on service calls is described by SST.
SST = SSR + SSresidual
SST = 76960.4 + 3416.38 = 80376.78
option A) is correct.
6) Rsq = 95.7% = 0.957
It expresses the propotion of variation in y which is explained by variation in number of copiers serviced.
Option c) is correct.
7) t statistic for X is 31.1 having P-value < = 0.0001
P-value < alpha (0.05)
Reject H0 at 5% level of significance.
The p-value for corresponding variable is highly significant.