Epidemiology: choosing a cut-off on the 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: choosing a cut-off on the ROC curve

Sample item

A screening programme picks the cut-off on an ROC curve that maximises the sum of sensitivity and specificity minus 1. What is this value called?

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

The answer and the reasoning

C. Youden index

The Youden index is sensitivity plus specificity minus 1, and the cut-off that maximises it is often chosen as the optimum. The area under the curve summarises overall discrimination. Kappa measures agreement beyond chance.

Option by option

  • A. Area under the curve

    The area under the curve describes overall test accuracy, not the choice of a point.

  • B. Positive predictive value

    Positive predictive value depends on prevalence and is not a cut-off criterion.

  • C. Youden index (correct)

    Correct. Youden index equals sensitivity plus specificity minus 1.

  • D. Kappa statistic

    Kappa measures agreement between observers or tests.

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 C, Youden index. The Youden index is sensitivity plus specificity minus 1, and the cut-off that maximises it is often chosen as the optimum.

Why is "Area under the curve" not the answer?

The area under the curve describes overall test accuracy, not the choice of a point.

Why is "Positive predictive value" not the answer?

Positive predictive value depends on prevalence and is not a cut-off criterion.

Why is "Kappa statistic" not the answer?

Kappa measures agreement between observers or tests.

What concept does this question test?

It tests Epidemiology: choosing a cut-off on the ROC curve in PSM. The area under the curve summarises overall discrimination. Kappa measures agreement beyond chance.

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: choosing a cut-off on the 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.