Lab 11

Lab 11 - Name: T.A. name/Class time: MW Lecturer: Lab 11:...

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Name: November 19, 2010 T.A. name/Class time: MW Lecturer: Lab 11: Chapter 11 The Federal Trade Commission annually rates varieties of domestic cigarettes according to their tar, nicotine, and carbon monoxide (CO) content. The United States Surgeon General considers each of these substances hazardous to a smoker's health. Past studies have shown that increases in the tar and nicotine content of a cigarette are accompanied by an increase in the carbon monoxide emitted from the cigarette smoke. The file “cigarettes.sav” on the course website contains data for 25 brands of cigarettes with the following variables: Brand name Tar content (mg) Nicotine content (mg) Weight (g) Carbon monoxide content (mg) Use this data set to determine the best multiple regression model for predicting the carbon monoxide content for a brand of cigarettes. Clearly state which explanatory variables remain in the best model. Check all regression assumptions and report the results. 1. (3 points) You should always start by looking at scatterplots of all the combinations of variables. Variables Form (linear or nonlinear) Direction (+ or -) Strength (strong, moderate, weak) Outliers? (yes/no, what country and values) Tar vs. Nicotine Tar vs. Weight Tar vs. CO Nicotine vs. Weight Nicotine vs. CO Weight vs. CO 1

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2. (1 point) Find the correlations between all of the pairs of variables. 3. (1 point) Which variable has the strongest correlation with carbon monoxide? 4. (1 point) Which variable is most weakly correlated with all the other variables? 5. (1 point) Why don’t we always just keep all the variables in the model and stop there? Note: Sometimes there is more than one best multiple regression model. There are even different procedures to use to find the best model: you can build your model up one variable at a time to find the model you want to keep, or you can start with a full model (using all the
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This note was uploaded on 11/08/2010 for the course STAT 301 taught by Professor Staff during the Spring '08 term at Purdue.

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Lab 11 - Name: T.A. name/Class time: MW Lecturer: Lab 11:...

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