Question 7.71

image 41. The Nurses’ Health Study has interviewed a sample of more than 100,000 female registered nurses every two years since 1976. Beginning in 1980, the study asked questions about diet, including alcohol consumption. The researchers concluded that “light-to- moderate drinkers had a significantly lower risk of death” than either nondrinkers or heavy drinkers.

  1. Is the Nurses’ Health Study an observational study or an experiment? Why?
  2. What does significant mean in a statistical report?
  3. Suggest some confounding variables that might explain why moderate drinkers have lower death rates than nondrinkers. (The study adjusted for these variables.)

41.

Sample response: (a) It is an observational study that gathers information (e.g., through interviews) without imposing any treatment.

(b) Significant means “unlikely to be due simply to chance.”

(c) Nondrinkers might be more elderly or in poorer health than moderate drinkers.