How to solve the problem a b and c? 8.15. Refer to Copier maintenance Problem 1.20. The users of the copiers are either training in- stitutions that use a small model, or business firms that use a large, commercial model. An analyst at Tri-City wishes to fit a regression model including both number of copiers serviced (X1) and type of copier (X2) as predictor variables and estimate the effect of copier model (S-small, L-large) on number of minutes spent on the service call. Records show that the models serviced in the 45 calls were: 1: 1 2 3 43 44 45 X 12: S L L LL L Assume that regression model (8.33) is appropriate, and let X = 1 if small model and 0 if large, commercial model. a. Explain the meaning of all regression coefficients in the model. b. Fit the regression model and state the estimated regression function. c. Estimate the effect of copier model on mean service time with a 95 percent confidence interval. Interpret your interval estimate. d. Why would the analyst wish to include X, number of copiers, in the regression model when interest is in estimating the effect of type of copier model on service time? e. Obtain the residuals and plot them against X,X2. Is there any indication that an interaction term in the regression model would be helpful? (10 points) KNNL 8.15. Instead of doing the parts. given in the problem, do the following: a. State the standard regression model that does not include interaction between the two predictors. Explain the meaning of 1 and B. b. State the standard regression model that includes the interaction between the two predictors. Explain the meaning of 2 (in terms of y-intercepts) and 3 (the coefficient for the interaction term). c. Fit both of the above models. Assuming the model assumptions are satisfied, what can you conclude? That is, provide your judgment as to whether there is a relationship between "copier type" and the response.