Biostatistics & Study Design USMLE Step 1 Practice Question
A rehabilitation study evaluates mobility outcomes in 47 elderly patients (mean age 72) using a 0–20 mobility scale. At baseline, 60% of highly functional participants score 20 despite varying functional abilities on direct observation. Post-intervention, the scale remains unchanged at 20 in these patients, while physical therapists document measurable gait speed improvements (0.3 m/s increase) and reduced fall risk. The scale fails to capture these objective gains. Which psychometric property best explains this limitation?
Answer choices
- ACeiling effectCorrect answer
- BVerification bias
- CFloor effect
- DAllocation concealment
- EConfounding
- FF. Construct validity
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