Question

10. Nested case-control studies:

A. use subjects drawn from a cohort study

B. provide a degree of control over confounding

C. reduce the cost of collecting exposure information

D. all of the above

13. Repeated cross-sectional surveys may underestimate past smoking behavior of older-age cohorts?

A. True

B. False

14. The purpose of the washout period is to reinforce the carryover effect.

A. True

B. False

18. Treatment crossover refers to any change of treatment for a patient in a clinical trial that involves a switch of study treatments.

A. True

B. False

Answer 1

10. Nested case-control studies:

D. all the above.

In nested case-control studies, the subjects are fully drawn from the cohort. The cost can be reduced by utilizing the data of the cohort study. It provides a degree of control among the cases.

13. Repeated cross-sectional surveys may underestimate past smoking behaviour of older-age cohorts?

A. True. The relative risk of disease among the exposed and the unexposed is a measure in the cohort study. The information may available only in rare cases.

14. The purpose of the washout period is to reinforce the carryover effect.

B. False.

A carryout period is an effect of treatment over the time period in response to the current period time. for example, if the patient receives drug A during the first period, and receives drug B during the second period, then the measurements taken for drug B is the effect of Drug B during the second period, and carryover of Drug A is the effect of Drug A during the first period of time. These effects result in statistical bias. The washout is the period of time between the Drug A and Drug B. But usually of stopping of Drug A, the Drug B has been started.

18. Treatment crossover refers to any change of treatment for a patient in a clinical trial that involves a switch of study treatments.

A. True.

The patient or the group may be switched from one treatment plan to another treatment plan during the course of the trial and after a pre-determined period of follow-up. The subjects may switch for various reasons. It may be planned or unplanned.