Biostatistics & Research · patient case question
Which study design is INTERVENTIONAL rather than observational?
Patient case: Patient who refuses whitening because of a cancer claim
Patient: Female, 38 years old
Chief Complaint: Interested in tooth whitening but has read online that it causes cancer.
Background: She raises the concern at consultation. The clinician wishes to find the best available evidence on whether vital tooth whitening is associated with oral cancer risk, in order to counsel her properly.
Current Findings: No relevant medical history. Generalised extrinsic staining. Sound dentition.
Show answer and explanation
Correct answer: D. A randomised controlled trial
- A. A cohort study follows groups defined by an exposure they already have. The investigator observes; they do not assign.
- B. A cross-sectional study measures exposure and outcome at a single point in time and is purely observational.
- C. A case-control study looks backward from outcome to exposure. It is observational and retrospective.
- D. CORRECT. In an interventional (experimental) study the investigator ASSIGNS the exposure. In a randomised controlled trial participants are allocated by chance to receive the intervention or the comparator, which is what makes it experimental. In all observational designs the investigator only watches what happens.
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