Epidemiology: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Epidemiology

Sample item

What is incidence density?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. New cases per unit person-time at risk

Incidence density expresses new events relative to accumulated person-time and is useful when follow-up durations differ between participants.

Option by option

  • A. All cases at one date

    Point prevalence counts existing cases.

  • B. Average hospital length of stay

    Length of stay is service utilization.

  • C. Deaths divided by births

    Deaths per births is a mortality measure.

  • D. New cases per unit person-time at risk (correct)

    Correct: person-time is the denominator.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More PSM questions

Questions about this PSM question

What is the answer to this PSM question?

The best answer is D, New cases per unit person-time at risk. Incidence density expresses new events relative to accumulated person-time and is useful when follow-up durations differ between participants.

Why is "All cases at one date" not the answer?

Point prevalence counts existing cases.

Why is "Average hospital length of stay" not the answer?

Length of stay is service utilization.

Why is "Deaths divided by births" not the answer?

Deaths per births is a mortality measure.

What concept does this question test?

It tests Epidemiology in PSM. The correct option holds because: Correct: person-time is the denominator.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Epidemiology?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.