Chapter 5.A, Problem 38E

Type of Study. Determine whether the following studies are observational studies or experiments. If the study is an experiment, identify the control and treatment groups, and discuss whether single-or double-blinding is necessary. If the study is observational, state whether it is a case-control study, and if so, identify the cases and controls.

38. A breast cancer study began by asking 25,624 women questions about how the spent their leisure time. The health of these women was tracked over the next 15 years. Those women who said they exercised regularly were found to have lower incidence of breast cancer (New England Journal of Medicine).