Table 1.

Common Types of Research using Existing Datasets

Research	Definition	Examples
Prospective study designs	Participants are enrolled prior to an event or exposure of interest and followed over time to determine effects or outcomes of the event or exposure.17	Clinical trials, data registries, and studies that follow individuals over time
Retrospective study designs	Exposure and covariate data are collected after the outcome has occurred (ie, the investigator is looking into the past to ascertain exposure status after collection of outcome data, rather than recruiting participants who are followed forward through time, as in a prospective study design).17	Case-control studies, retrospective cohort studies, studies using vital statistics from birth records
Secondary data analysis	Research using existing data to answer question(s) that are different from the original purposes or questions that motivated data collection.18 Secondary data analysis may be conducted using prospectively-collected data or data not collected for research.	Analysis of data from a previous cohort study or randomized trial, or claims data analysis
Administrative data research	Studies analyzing data collected for administrative purposes rather than explicitly for research. Administrative data are collected routinely for legal, compliance, or official government or institutional purposes. Research using administrative data is a type of secondary data research.	Studies involving regulatory compliance measurement (eg, air quality measures), census data, information from vital records