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Biostatistics — Step 1 practice questions
274 questions in this area, with an explanation for every answer choice.
Three samples below, free and without an account.
How this shows up on Step 1
The most self-contained discipline on the exam, and the most reliably scorable. Study design, measures of association, and diagnostic test characteristics dominate. Because it needs no clinical knowledge, it is the section most worth securing early.
Sample questions
Sample question 1
At what age does average-risk colorectal cancer screening typically begin according to current general guidelines?
Explanations
A. Age 65
Age 65 is later than the recommended starting age for average-risk screening.
B. Age 45 · correct
Current general guidelines recommend average-risk colorectal cancer screening beginning at age 45 (lowered in recent years from the previously recommended age 50, due to rising rates in younger populations).
C. Age 80
Age 80 is well beyond the typical starting age; screening is generally initiated much earlier, with decisions about STOPPING screening being individualized at older ages.
D. Screening is never recommended for average-risk individuals
Screening is indeed recommended for average-risk individuals starting at the appropriate age.
E. Age 30
Age 30 is earlier than the current general average-risk screening recommendation.
Sample question 2
A blood pressure cuff consistently reads 15 mm Hg higher than the true value on repeated measurements. Which of the following best describes this instrument?
Explanations
A. Neither reliable nor valid
The measurements are consistent, so reliability is preserved.
B. Valid but not reliable
Consistency indicates reliability; the systematic offset destroys validity.
C. Both reliable and valid
A systematic 15 mm Hg error is not valid.
D. Reliable but not valid, since it produces consistent results that are systematically incorrect · correct
RELIABILITY (precision) is reproducibility — consistency on repeated measurement — and is threatened by RANDOM error. VALIDITY (accuracy) is closeness to the truth and is threatened by SYSTEMATIC error, or bias. A cuff reading consistently 15 mm Hg high is highly reliable but invalid, illustrating that reliability is necessary but not sufficient for validity. The dartboard analogy is standard: tightly clustered darts far from the bullseye are precise but inaccurate.
E. Precision and accuracy are equivalent concepts, so it is simply inaccurate
The concepts are distinct and both apply.
Sample question 3
A screening program must invite 1,000 people over 10 years to prevent one death from the target cancer. Which of the following best describes how this should be communicated?
Explanations
A. Discourage all screening because the number needed to screen is large
A large number needed to screen can still represent worthwhile population benefit.
B. Present only the relative mortality reduction, which is more motivating
Relative figures alone distort perceived benefit.
C. Present the absolute benefit alongside the harms — false positives, additional procedures, and overdiagnosis — so individuals can weigh both in a preference-sensitive decision · correct
Screening decisions are preference-sensitive, and honest communication requires presenting benefits and harms in the SAME absolute terms over the SAME time horizon — for instance, per 1,000 people screened over 10 years, how many avoid a cancer death, how many receive a false positive, how many undergo biopsy, and how many are overdiagnosed and treated for disease that would never have surfaced. Presenting only relative reductions inflates perceived benefit and undermines informed choice. Decision aids substantially improve knowledge and decisional quality.
D. Recommend screening universally without discussing harms
Screening carries real harms requiring disclosure.
E. Screening harms are negligible and need not be discussed
False positives, procedural complications, and overdiagnosis are substantive harms.
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