Refer to Examples 6€“8 on nicotine dependence for teenage smokers. Another explanatory variable was whether a subject reported inhaling when smoking. The table reports descriptive statistics.

a. Explain why (i) the overwhelming majority of noninhalers must have had HONC scores of 0 and (ii) on average, those who reported inhaling answered yes to nearly three more questions than those who denied inhaling.
b. Might the HONC scores have been approximately normal for each group? Why or why not?
c. Find the standard error for the estimate (1 - 2) = 2.8. Interpret.
d. The 95% confidence interval for (μ1 - μ2) is (2.3, 3.3). What can you conclude about the population means for inhalers and noninhalers?

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HONC Score Mean Standard Deviation Croup Sample sSife Inhalers 237 95 2.9 0.1 3.6 0.5 Noninhalers