A 30-month study evaluated the degree of addiction that teenagers form to nicotine once they begin experimenting with smoking.16 The study used a random sample of 332 seventh-grade students in two Massachusetts cities who had ever used tobacco by the start of the study. The response variable was constructed from the Hooked on Nicotine Checklist (HONC), a list of 10 questions such as

“Have you ever tried to quit but couldn’t?” The HONC score is the total number of questions to which a student answered yes. At the end of the study, the HONC means describing nicotine addiction were 5.9 (s = 3.3) for the 75 smokers and 1.0 (s = 2.3) for the 257 ex-smokers.

(a) Software reports a 95% confidence interval of (4.1, 5.7). Interpret.

(b) Was the HONC sample data distribution for exsmokers approximately normal? How does this affect inference? Why?