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Unformatted text preview: STAT5044: Regression and ANOVA Homework #4 Problem# 1. A large, national grocery retailer tracks productivity and costs of its facilities closely. Data were obtained from a single distribution center for a one- year period. Each data point for each variable represents one week of activity. The variables included are the number of cases shipped ( X 1 ), the indirect costs of the total labor hours as a percentage ( X 2 ), a qualitative predictor called holiday that is coded 1 if the week has a holiday and o otherwise ( X 3 ), and the total labor hours ( Y ) (a) Fit multiple linear regression model to the data for three predictor variables. State the estimated regression function. How are b 1 , b 2 , and b 3 interpreted here? (b) Obtain the residuals and prepare a box plot of the residuals. What information does this plot provide? (c) Plot the residuals against Y , X 1 , X 2 , X 3 , and X 1 X 2 on separate graphs. Also prepare a normal probability plot. Interpret the plots and summarize your findings. (d) Prepare a time plot of the residuals. Is there any indication that the error terms are correlated. Discuss. (In this problem, time plot is the plot(c(1:n), residuals) in R, where n is the total sample size) (e) Divide the 52 cases into two groups, placing the 26 cases with the smallest fitted...
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This note was uploaded on 01/02/2012 for the course STAT 5044` taught by Professor Staff during the Fall '11 term at Virginia Tech.
- Fall '11