What are the two broad categories of explanatory (analytic) studies?

• A. Descriptive and analytic
• B. Observational (cohort, case-control, cross-sectional, hybrid) and experimental (laboratory and clinical trials)
• C. Qualitative and quantitative
• D. Case series and case reports

Answer: (B)

Analytic studies aim to examine associations or causal effects and fall into two broad categories: observational and experimental. In observational studies, researchers observe exposures and outcomes as they occur in the real world without assigning exposures to participants. Examples include cohort studies, case-control studies, cross-sectional studies, and hybrid designs like nested case-control or case-cohort within a cohort. In experimental studies, the investigator actively assigns the exposure and controls conditions to test its effect, such as in laboratory experiments or clinical trials, often with randomization to reduce confounding. Descriptive studies and designs focused on data type (qualitative vs quantitative) or case reports/series don’t constitute the analytic categories used for testing hypotheses about associations or causation.