Evidence of an increased risk of lung cancer associated with cigarette smoking was sought by Doll and Hill. In one study, 649 lung cancer cases were matched by age, and gender to 649 controls; 647 of the cases and 622 of the control had a history of smoking cigarettes.

Question

a. Name the type of study.
b. Create the appropriate 2X2 table for the study.

Lung Cancer Controls
Smokers 647 622
Nonsmokers 2 27
Total 649 649

c. Calculate the appropriate measure of association for the study.
d. Interpret the results.

Answer 1

a. Matched pairs

c. Use the Chi-square (X^2) method.

X^2 = ∑ (O-E)^2/E, where O = observed frequency and E = expected frequency.

∑ = sum of all the cells.

E = (column total * row total)/grand total

df = n - 1, where n = number of cells

Look up value in X^2 table in the back of your textbook.

d. I'll let you come to your own conclusions.