Which option is NOT considered a descriptive study type?

• A. Case report
• B. Case series
• C. Survey
• D. Randomized trial

Answer: (D)

Descriptive studies focus on describing who, where, and when health events occur, without testing causal hypotheses. A case report describes a single patient, and a case series summarizes several patients with the same condition, both of which document observations. A survey, often cross-sectional, collects data to describe the prevalence and distribution of attributes or diseases in a population. A randomized trial, by contrast, assigns participants to receive an intervention or control and compares outcomes to evaluate the effect of that intervention. This introduces an experimental element aimed at testing causality and intervention effectiveness, not merely describing patterns. Therefore, the randomized trial is not a descriptive study type.