Week 5: Epidemiology Study Designs: Cohort, Experimental, and Quasi-Experiments

What is a cohort study?

An observational study that follows a defined group over time and compares exposed vs. unexposed groups.

What do cohort studies measure?

Incidence, risk, and outcomes.

What does temporality mean?

The exposure occurs before the outcome.

What is a prospective cohort study?

Participants are followed forward in time.

What is a retrospective cohort study?

Past records are used to study exposures and outcomes.

What is a nested case-control study?

A case-control study conducted within an existing cohort.

What is a longitudinal cohort study?

Participants are repeatedly followed over a long period.

What is the major difference between cohort and experimental studies?

Cohort studies observe; experimental studies intervene.

What is an experimental study?

A study where researchers assign an exposure or intervention and compare intervention vs. control groups.

What are the key features of experimental studies?

Intervention, randomization, control/comparison groups, and blinding.

Why is randomization used?

To reduce confounding.

Why is blinding used?

To minimize bias.

What is an RCT?

Participants are randomly assigned to intervention vs. control groups.

What is a field trial?

A preventive intervention tested in a real-world, non-clinical setting.

What is a community trial?

An intervention applied at the population or community level.

What is a quasi-experimental/natural experiment?

A study where the researcher does not control exposure and there is no randomization.

Researchers follow nurses from 2020-2040 to see who develops breast cancer. What design?

Prospective cohort.

Researchers review old employee records for asbestos exposure and lung disease. What design?

Retrospective cohort.

Participants are randomly assigned to a vaccine or placebo. What design?

RCT.

A vaccine is tested among schoolchildren in an endemic village. What design?

Field trial.

A smoking intervention is applied at the city level. What design?

Community trial.

Researchers study the effect of a soda tax with no randomization. What design?

Quasi-experimental/natural experiment.