Retrospective study is defined as an observational study in which subjects are selected and then their previous conditions or behaviors are determined

Retrospective study is defined as an observational study in which subjects are selected and then their previous conditions or behaviors are determined

• A. An observational study in which subjects are selected and then their previous conditions or behaviors are determined
• B. A cross-sectional survey at a single point in time
• C. A randomized controlled trial
• D. A study that follows participants over time

Answer: (A)

Retrospective studies look backward in time. You start with a group of subjects and then determine their past conditions or exposures from records or recall. This observational approach means there’s no new intervention, and the study often compares those with a particular outcome to those without to see how their past exposures might differ. That’s why this description fits retrospective designs well, especially classic case-control studies that select by outcome and look back at prior exposures. By contrast, a cross-sectional survey measures exposure and outcome at a single moment in time, providing a snapshot without establishing temporality. A randomized controlled trial involves actively intervening and assigning participants to groups, which is experimental rather than observational. A study that follows participants over time describes a longitudinal or prospective cohort design, observing outcomes as they occur going forward.

Retrospective studies look backward in time. You start with a group of subjects and then determine their past conditions or exposures from records or recall. This observational approach means there’s no new intervention, and the study often compares those with a particular outcome to those without to see how their past exposures might differ. That’s why this description fits retrospective designs well, especially classic case-control studies that select by outcome and look back at prior exposures.

By contrast, a cross-sectional survey measures exposure and outcome at a single moment in time, providing a snapshot without establishing temporality. A randomized controlled trial involves actively intervening and assigning participants to groups, which is experimental rather than observational. A study that follows participants over time describes a longitudinal or prospective cohort design, observing outcomes as they occur going forward.