Another cigarette. Consider again the regression of Nicotine content on Tar (both in milligrams) for the cigarettes examined in given Exercise.

a) What is the correlation between Tar and Nicotine?

b) What would you predict about the average Nicotine content of cigarettes that are 2 standard deviations below average in Tar content?

c) If a cigarette is 1 standard deviation above average in Nicotine content, what do you suspect is true about its Tar content?

Exercise:
Cigarettes. Is the nicotine content of a cigarette related to the "tars"? A collection of data (in milligrams) on 29 cigarettes produced the scatterplot, residuals plot, and regression analysis shown:

a) Do you think a linear model is appropriate here? Explain.

b) Explain the meaning of R² in this context.