Biostatistics: interpreting the p-value: 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: interpreting the p-value

Sample item

A trial reports that a new regimen lowers HbA1c compared with standard care, with p = 0.03. Which is the correct interpretation?

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

The answer and the reasoning

D. If there were truly no difference, a difference at least this large would arise by chance in about 3% of repeated studies

The p-value is the probability of obtaining the observed result, or one more extreme, if the null hypothesis were true. It does not give the probability that either hypothesis is true and says nothing about the size or clinical importance of the effect. Effect size and confidence intervals convey that information.

Option by option

  • A. There is a 3% probability that the null hypothesis is true

    The p-value is computed assuming the null is true; it is not the probability of the null.

  • B. The regimen lowers HbA1c by 3% on average

    The magnitude of the effect is given by the mean difference, not by the p-value.

  • C. There is a 97% probability that the regimen works

    The p-value does not give the probability that the alternative hypothesis is true.

  • D. If there were truly no difference, a difference at least this large would arise by chance in about 3% of repeated studies (correct)

    Correct. This is the definition of a p-value under the null hypothesis.

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, If there were truly no difference, a difference at least this large would arise by chance in about 3% of repeated studies. The p-value is the probability of obtaining the observed result, or one more extreme, if the null hypothesis were true.

Why is "There is a 3% probability that the null hypothesis is true" not the answer?

The p-value is computed assuming the null is true; it is not the probability of the null.

Why is "The regimen lowers HbA1c by 3% on average" not the answer?

The magnitude of the effect is given by the mean difference, not by the p-value.

Why is "There is a 97% probability that the regimen works" not the answer?

The p-value does not give the probability that the alternative hypothesis is true.

What concept does this question test?

It tests Biostatistics: interpreting the p-value in PSM. It does not give the probability that either hypothesis is true and says nothing about the size or clinical importance of the effect. Effect size and confidence intervals convey that information.

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: interpreting the p-value?

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.