Which of the following are three types of descriptive studies?

• A. Cohort study, case-control, cross-sectional
• B. Randomized trial, cohort, case report
• C. Case report, case series, surveys
• D. Systematic review, meta-analysis, narrative review

Answer: (C)

Descriptive studies document what is happening in a population or group without testing hypotheses or comparing groups. They focus on describing who is affected, how often, and where or when. Case reports describe detailed information about a single patient, highlighting unusual or new presentations. Case series extend that to a few patients with the same condition, noting patterns across cases. Surveys collect data from a sample to describe characteristics such as prevalence or health behaviors at a given time, often in a cross-sectional manner. These are classic descriptive approaches because they summarize and describe data rather than test associations or cause-effect relationships. In contrast, analytic designs like cohort or case-control delve into associations, randomized trials test interventions, and systematic reviews or meta-analyses synthesize existing studies rather than generating new descriptive data. Therefore, case report, case series, and surveys are the descriptive trio.