# Statistics 227

## Autumn, 1995Final Exercise

Due Wednesday, 13 December 1995
5:00 pm at Eckhart 126

Last updated 6 December 95, 11:00 am CST

For this assignment, collaboration and discussion are not permitted. You may use any published source on any topic. If you use any outside sources, be sure to cite them in your paper. Do not discuss these problems with other individuals, including people who are not taking the course. You may direct questions to RT, who will provide an answer when it is appropriate to do so.

1. [Smoking] (Source: Rosner)

"A study was conducted among 234 people who had expressed a desire to stop smoking but who had not yet stopped. On the day they quit smoking, their carbon monoxide level (CO) was measured and the time was noted from the time they smoked their last cigarette to the time of the CO measurement. The CO level provides an "objective" indicator of the number of cigarettes smoked per day during the time immediately prior to the quit attempt. However, it is known to also be influenced by the time since the last cigarette was smoked. Thus, this time is provided, as well as a "corrected CO level," which is adjusted for the time since last smoked. Information is also provided on the age and sex of the subjects, as well as the subject's self-report of the number of cigarettes per day.

"The subjects were followed up for one year for the purpose of determining the number of days they remained abstinent. The number of days abstinent ranges from 0 for those who quit for less than 1 day to 365 days for those who were abstinent for the full year."

The data consist of the following variables on each subject:

```ID numer
Age
Sex (1=male, 2=female)
Cigarettes/day (self report)
Carbon monoxide level (CO)  [x10]
Minutes elapsed since the last cigarette smoked
Days abstinent
```
Missing values are denoted by "." in the data set.

Is there anything that will predict success in quitting (say, by being abstinent for at least 3 weeks)? For those who can abstain for three weeks, what factors predict ultimate success (one-year abstinence)?

The data set is located in the file smoke2.dat in the "Other Data Sets" location on the Web page. Your submission should consist of at most two typewritten pages, including any tables or figures.

2. []