1. **State the problem:** We are analyzing a study about colon cancer screening programs and their effect on death rates from colon cancer. 2. **Identify the type of study:** The study is observational because the researchers did not randomly assign participants to screening or nonscreening groups; they observed existing groups. 3. **Identify variables:** - Response variable: rate of death from colon cancer. - Explanatory variable: whether or not there was a screening program. 4. **Interpret causation:** Since this is an observational study, it cannot prove causation. There may be lurking variables affecting both screening and death rates. 5. **Answer to part c:** The correct choice is D: No, a lurking variable may exist that influences both variables. This means the study found an association but not definitive proof of causation.