Epidemiology: attributable risk: 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: attributable risk

Sample item

In a cohort, the incidence of lung cancer is 20 per 1,000 in smokers and 5 per 1,000 in non-smokers. What percentage of cancer among smokers is attributable to smoking?

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

The answer and the reasoning

A. 75 percent

Attributable risk is 20 minus 5, which is 15 per 1,000. Attributable risk percent is 15 divided by 20 times 100, giving 75 percent. This is the proportion of disease in the exposed that could be removed by eliminating exposure.

Option by option

  • A. 75 percent (correct)

    Correct. (20 minus 5) divided by 20 is 75 percent.

  • B. 400 percent

    400 percent is the relative risk expressed as a percentage.

  • C. 15 percent

    15 is the absolute attributable risk per 1,000, not a percentage.

  • D. 25 percent

    25 percent is the proportion due to causes other than smoking.

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 A, 75 percent. Attributable risk is 20 minus 5, which is 15 per 1,000.

Why is "400 percent" not the answer?

400 percent is the relative risk expressed as a percentage.

Why is "15 percent" not the answer?

15 is the absolute attributable risk per 1,000, not a percentage.

Why is "25 percent" not the answer?

25 percent is the proportion due to causes other than smoking.

What concept does this question test?

It tests Epidemiology: attributable risk in PSM. Attributable risk percent is 15 divided by 20 times 100, giving 75 percent. This is the proportion of disease in the exposed that could be removed by eliminating exposure.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: attributable risk?

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.