This table comes from one of the first studies of the link between lung cancer and smoking, by Richard Doll and A. Bradford Hill. In 20 hospitals in London, UK, patients admitted with lung cancer in the previous year were queried about their smoking behavior. For each patient admitted, researchers studied the smoking behavior of a noncancer control patient at the same hospital of the same sex and within the same 5 year grouping on age. A smoker was defined as a person who had smoked at least one cigarette for a year.

1. State the response and explanatory variables. Justify your answer

2. Explain why it is not possible to estimate the proportion of the population having lung cancer from the study data. (Caution: It is not enough to say it is a retrospective

3) Using the fact that the proportion of the population having lung cancer is low, estimate the relative risk of lung cancer for having smoked versus not having smoked. Set up a calculation for this estimate. Do not complete the computation. Justify your reasoning.

Have Smoked Yes No Total Cases 688 21 709 Lung Cancer Controls 650 59 709