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Assignment #4
(Due: March 11, 2011)
1. To combat automobile pollution, research is underway to determine the chemical composition of a
gasoline additive that will improve emission quality. One aspect of investigation is to study the
relationship between the amount of a particular additive and the reduction in the emission of nitrogen
oxides. Ten (10) new Mustangs are selected as the experimental units. We would like to study the
relationship between the amount of additive (add = X) and the reduction (reduce = Y) in the emission of
nitrogen oxides. See the
AutoPoll.txt.
a. Compute the Pearson correlation coefficient between Additive and Reduction. Is this significant?
b. Fit a simple linear regression. What are the slope and intercept and their 95% confidence intervals?
Are they significantly different from zero? What is your estimate for the standard deviation of the error?
c. Generate a plot of the original data, the regression line and the 95% confidence interval and
prediction band on the same set of axes.
d. What are the predicted values for Additive = 3.5 and 4.5? What are the confidence and prediction
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 Spring '11
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