24 Chapter 1 Basic Ideas Case-control studies are always retrospective, because the outcome (case or control) has occurred before the sampling is done. Case-control studies have the same advantages and disadvantages as retrospective cohort studies. In addition, case-control studies have the advantage that they can be used to study rare diseases. Check Your Understanding 3. In a study conducted at the University of Southern California, J. Peters and colleagues studied elementary school students in 12 California communities. Each year for 10 years, they measured the respiratory function of the children and the levels of air pollution in the communities. a. Was this a cohort study or a case-control study? b. Was the study prospective, cross-sectional, or retrospective? 4. In a study conducted at the University of Colorado, J. Ruttenber and colleagues studied people who had worked at the Rocky Flats nuclear weapons production facility near Denver, Colorado. They studied a group of workers who had contracted lung cancer, and another group who had not contracted lung cancer. They looked back at plant records to determine the amount of radiation exposure for each worker. The purpose of the study was to determine whether the people with lung cancer had been exposed to higher levels of radiation than those who had not gotten lung cancer. a. Was this a cohort study or a case-control study? b. Was the study prospective, cross-sectional, or retrospective? Answers are on page 26. SECTION 1.3 Exercises Exercises 1–4 are the Check Your Understanding exercises located within the section. Understanding the Concepts In Exercises 5–10, fill in each blank with the appropriate word or phrase. 5. In a experiment, subjects do not decide for themselves which treatment they will get. 6. In a study, neither the investigators nor the subjects know who is getting which treatment. 7. A study in which the assignment to treatment groups is not made by the investigator is called . 8. A is a variable related to both the treatment and the outcome. 9. In a study, the subjects are followed over time. 10. In a study, a group of subjects is studied to determine whether various factors of interest are associated with an outcome. In Exercises 11–16, determine whether the statement is true or false. If the statement is false, rewrite it as a true statement. 11. In a randomized experiment, the treatment groups do not differ in any systematic way except that they receive different treatments. 12. A confounder makes it easier to draw conclusions from a study. 13. In an observational study, subjects are assigned to treatment groups at random. 14. Observational studies are generally more reliable than randomized experiments. 15. In a case-control study, the outcome has occurred before the subjects are sampled. 16. In a cross-sectional study, measurements are made at only one point in time. Practicing the Skills 17. To determine the effectiveness of a new pain reliever, a randomly chosen group of pain sufferers is assigned to take the new drug, and another randomly chosen group is assigned to take a placebo. a. Is this a randomized experiment or an observational study? b. The subjects taking the new drug experienced substantially more pain relief than those taking the placebo. The research team concluded that the new drug is effective in relieving pain. Is this conclusion well justified? Explain. 18. A medical researcher wants to determine whether exercising can lower blood pressure. At a health fair, he measures the blood pressure of 100 individuals, and interviews them about their exercise habits. He divides the individuals into two categories: those whose typical level of exercise is low, and those whose level of exercise is high. a. Is this a randomized experiment or an observational study?
navidi_monk_essential_statistics_1e_ch1_3
To see the actual publication please follow the link above