Biostatistics: test for paired proportions: 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 · Biostatistics: test for paired proportions

Sample item

The same 150 patients are tested with a rapid test and with an ELISA. The investigator wants to know whether the proportion testing positive differs between the two tests. Which test of significance suits these paired binary data?

ALog-rank testBMcNemar testCUnpaired t testDOne-way ANOVA

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

The answer and the reasoning

B. McNemar test

When the same subjects are measured twice with a binary outcome, the data are paired and the McNemar test uses only the discordant pairs. An unpaired approach ignores the pairing. It is the paired analogue of the chi-square test.

Option by option

A. Log-rank test
The log-rank test compares time-to-event curves.
B. McNemar test (correct)
Correct. McNemar test compares paired proportions through discordant pairs.
C. Unpaired t test
An unpaired t test compares means of a continuous variable in independent groups.
D. One-way ANOVA
ANOVA compares means across three or more groups.

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.

Questions about this PSM question

What is the answer to this PSM question?

The best answer is B, McNemar test. When the same subjects are measured twice with a binary outcome, the data are paired and the McNemar test uses only the discordant pairs.

Why is "Log-rank test" not the answer?

The log-rank test compares time-to-event curves.

Why is "Unpaired t test" not the answer?

An unpaired t test compares means of a continuous variable in independent groups.

Why is "One-way ANOVA" not the answer?

ANOVA compares means across three or more groups.

What concept does this question test?

It tests Biostatistics: test for paired proportions in PSM. An unpaired approach ignores the pairing. It is the paired analogue of the chi-square test.

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 Biostatistics: test for paired proportions?

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.