Epidemiology: ROC curve: 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: ROC curve

Sample item

A receiver operating characteristic (ROC) curve is plotted with which axes?

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

The answer and the reasoning

D. Sensitivity on Y axis against 1 minus specificity on X axis

The ROC curve plots the true positive rate (sensitivity) against the false positive rate (1 minus specificity) for different cut-offs. A test with greater area under the curve discriminates better.

Option by option

  • A. Sensitivity against false negative rate

    Sensitivity and false negative rate are complementary and would give a straight line.

  • B. Positive predictive value against prevalence

    Predictive value versus prevalence is a different relationship.

  • C. Specificity on Y axis against sensitivity on X axis

    The axes are not specificity versus sensitivity in this arrangement.

  • D. Sensitivity on Y axis against 1 minus specificity on X axis (correct)

    Correct. This is the standard ROC definition.

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.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is D, Sensitivity on Y axis against 1 minus specificity on X axis. The ROC curve plots the true positive rate (sensitivity) against the false positive rate (1 minus specificity) for different cut-offs.

Why is "Sensitivity against false negative rate" not the answer?

Sensitivity and false negative rate are complementary and would give a straight line.

Why is "Positive predictive value against prevalence" not the answer?

Predictive value versus prevalence is a different relationship.

Why is "Specificity on Y axis against sensitivity on X axis" not the answer?

The axes are not specificity versus sensitivity in this arrangement.

What concept does this question test?

It tests Epidemiology: ROC curve in PSM. A test with greater area under the curve discriminates better.

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: ROC curve?

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.