13.31 Carbon aerosols have been identified as a contributing factor in a number of air quality problems.

Question:

13.31 Carbon aerosols have been identified as a contributing factor in a number of air quality problems.

In a chemical analysis of diesel engine exhaust, x 5 mass

(mg/cm2) and y 5 elemental carbon (mg/cm2) were recorded

(“Comparison of Solvent Extraction and Thermal Optical Carbon Analysis Methods: Application to Diesel Vehicle Exhaust Aerosol” Environmental Science Technology [1984]: 231– 234). The estimated regression line for this data set is y^ 5 31 1 .737x. The accompanying table gives the observed x and y values and the corresponding standardized residuals.

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x 78.9 387.8 135.0 82.9 117.9 y 86 310 141 90 130 St. resid. 20.27 20.89 0.91 20.18 1.05

a. Construct a standardized residual plot. Are there any unusually large residuals? Do you think that there are any influential observations?

b. Is there any pattern in the standardized residual plot that would indicate that the simple linear regression model is not appropriate?

c. Based on your plot in Part (a), do you think that it is reasonable to assume that the variance of y is the same at each x value? Explain.

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Related Book For  book-img-for-question

Introduction To Statistics And Data Analysis

ISBN: 9780840054906

4th Edition

Authors: Roxy Peck, Chris Olsen, Jay L. Devore

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