Relationship between cigarette smoking and lung cancer

Part 1:
The following table shows the relationship between cigarette smoking and lung
cancer among male cases and controls:
Table 1
Cases Controls
Cigarette
Smoker 1,350 1,296
Nonsmoker 7 61
Total 1,357 1,357
1. Accurately calculate the proportion of cases that smoked. Be sure to show
your calculations.
Answer
Proportion of cases that smoked= 1350
1357 =0.9948∨99.48 %
2. Accurately calculate the proportion of controls that smoked. Be sure to show
your calculations.
Answer
Proportion of cases that smoked= 1296
1357 =0.9550∨95.50 %
3. Accurately calculate the odds ratio, with the correct equation. What do you
infer from the odds ratio about the relationship between smoking and lung
cancer?
Answer
Odds ratio= a∗d
b∗c
Odds ratio= 1350∗61
1296∗7 =82350
9072 =9.077
From the above computations, we can see that the odds ratio is 9.077. This
suggests that the odds are higher that an individual will develop lung cancer
if such a person is a smoker (Kligerman & White, 2011). The likelihood of
developing lung cancer is approximately 9 times higher in smokers as
compared to non-smokers.
Table 2 shows the frequency distribution of male cases and controls by
average number of cigarettes smoked per day. Table 2: Daily cigarette
consumption
Daily number of
cigarettes
Number of cases Number of controls
0 7 61
1-14 565 706

15-24 445 408
25+ 340 182
All smokers 1350 1296
Total 1357 1357
4. Accurately calculate the odds ratios by category of daily cigarette
consumption, comparing each category to nonsmokers. Be sure to show your
calculations.
Answer
34465
4942 =6.97
27145
2856 =9.50
20740
1274 =16.28
82350
9072 =9.077
82777
9499 =8.71
Daily number of
cigarettes
Number of cases Number of
controls
Odds ratio
0 7 61 Referent
1-14 565 706 6.97
15-24 445 408 9.50
25+ 340 182 16.28
All smokers 1350 1296 9.077
Total 1357 1357 8.71
5. Interpret these results, and describe the trends or patterns you see in the
data.
Answer
The above results shows that the odds ratio increases with increase in the
number of daily cigarettes smoked.
Part 2: The Cohort Study
Table 3: Number and rate (per 100,000 person-years) of lung cancer deaths by
number of cigarettes smoked per day, Doll and Hill physician cohort study, Great
Britain, 1951–1961.