Retrospective research designs
Retrospective research designs are used when the outcome has already occurred
There are certain instances where these designs should be employed. Case series designs are basic science projects where hypotheses are generated and effect sizes are established. Case-control designs should be employed for very rare outcomes and hypothesis generation. Because of the amount of observation and selection bias associated with selecting control participants and using existing data, case series and case-control designs yield the lowest levels of empirical evidence. However, if a researcher is traversing new empirical territory or looking for potential predictors of disease states, these designs are feasible. Pilot studies with at least 150-300 participants or observations can establish effect sizes for conducting a priori sample size calculations for higher-level studies.
The retrospective cohort design is the most powerful retrospective observational design in terms of the evidence yielded. They test associations associated with exposures and outcomes and can be used to assess temporal components of disease states.
Types of retrospective observational designs
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