In density-sampled case-control studies, a person who is selected as a control who then remains in the study population and at risk for developing the outcome should remain eligible to be selected as a control a second time.

Question

BlackTom AI · Accepted Answer

In density-sampled (risk-set) case-control studies, controls are selected from individuals who are at risk at the time each case occurs. This design allows controls to be sampled multiple times for different cases, as long as they remain at risk when each case arises.
Option 1: True. This statement aligns with the principle of density (risk-set) sampling, where a person who is selected as a control and continues to be at risk can indeed be chosen again as a control for future cases. The sampling is conditional on the risk set at each case time, not on a fixed, one-time selection.
Option 2: False. This would imply that repeat selection as a control is prohibited, or that individuals cannot be chosen again once selected, which contradicts the standard practice of density sampling where the same at-risk individual may appear as a control for multiple cases over the study period. Misconceptions here might treat controls as a fixed cohort rather than a dynamic risk set.
Option 3: True. Another way to state the same concept is that the control selection is time-mpecific and the sampling can reinclude the same individual if they remain at risk when another case occurs, reflecting the independence between case times and control draws across the risk sets.
Option 4: False. If one believes that controls are drawn once and cannot be reselected, that would be a misunderstanding of risk-set sampling, which permits multiple selections across different case times as long as eligibility criteria are met at each time point.

In density-sampled case-control studies, a person who is selected as a control who then remains in the study population and at risk for developing the outcome should remain eligible to be selected as a control a second time.判断题

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