hw4_05 - • Leverage Values • DFFITS • DFBETAS Which...

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STA 6127 – Homework #4 Model Building – Due 3/28/08 1) For the Crime data, we have the following variables (all are approximately the year 1990): Y = SERCRM (Total # of Serious Crimes in County/1000 Population) X 1 = DO1619 (Percent Current HS Dropouts High School Dropouts – Ages 16-19) X 2 = COLLDG25 (Percent Adults with College Degrees) X 3 = PCInc(Per capita income in $1000s) X 4 = PctPov (Percent of People Below Poverty Level in County) X 5 = BrthperK (Births per 1000) X 6 = DivperK (Divorces per 1000) a) Using Backward Elimination with SLS=0.10 , which predictors do you include in your regression model? b) Using Forward Selection with SLE=0.10 , which predictors do you include in your regression model? c) Using Stepwise Regression with SLE=0.100 and SLS=0.101 , which predictors do you include in your regression model? d) Obtain the following regression diagnostic measures for each observation, based on your model from part c): Studentized Residuals
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Unformatted text preview: • Leverage Values • DFFITS • DFBETAS Which Counties are “problem counties” with respect to each measure? Why? e) Plot the studentized residuals ( *SRESID on Y-axis) vs standardized predicted values ( *ZPRED on X-axis). Is there evidence of the residual variance being related to the mean of the response? Why? f) Obtain a histogram of the standardized residuals. Do they appear to be approximately normally distributed. g) Fit the regression model with all k =6 predictors. Obtain the Variance Inflation Factors. Is multicollinearity a problem? Give the regression coefficients and standard errors for all terms. Compare these with the model from c), including Variance Inflation Factors. Put N/A under reduced model for variables not included in model. Full Model ( k =6 predictors) Reduced Model (from part c) Predictor Coeff Std. Error VIF Coeff Std. Error VIF X 1 X 2 X 3 X 4 X 5 X 6...
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This note was uploaded on 01/20/2012 for the course STA 6127 taught by Professor Mukherjee during the Spring '08 term at University of Florida.

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hw4_05 - • Leverage Values • DFFITS • DFBETAS Which...

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