In another study, the smoking habits of 34,445 male physicians were obtained by mailed questionnaires. Deaths among these physicians over the subsequent years were identified though contact with the office of the Registrar General. The death rates from lung cancer of these physicians classified by smoking habits were :

Standardized Death Rates per 1000 Persons Aged 35 or More per Year
Nonsmokers 0.07
Cigarette Smokers 0.96

a. Name the type of study.
b. Calculate the Relative Risk for smokers as compared to nonsmokers.

c. Interpret the results

a. The type of study described is an observational study.

b. To calculate the Relative Risk (RR) for smokers as compared to nonsmokers, we need to divide the death rate of smokers by the death rate of nonsmokers.

RR = Death rate of smokers / Death rate of nonsmokers

RR = 0.96/0.07

c. To interpret the results, we compare the relative risk value to 1.

If RR > 1: It indicates that smokers have a higher risk of death from lung cancer compared to nonsmokers. In this case, the RR is approximately 13.7 (0.96/0.07), which means that smokers have a 13.7 times higher risk of death from lung cancer compared to nonsmokers.

If RR = 1: It indicates that smokers have the same risk of death from lung cancer as nonsmokers.

In this study, the relative risk suggests a substantially higher risk of death from lung cancer among smokers compared to nonsmokers.