Biostatistics: statistical versus clinical significance: 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: statistical versus clinical significance

Sample item

A trial of 20,000 patients reports that a new drug lowers mean systolic pressure by 0.5 mmHg compared with placebo, with p less than 0.001. How should this finding be interpreted?

AIt shows that the drug lacks any biological effectBIt is clinically important because the p value is very smallCIt is neither statistically nor clinically significantDIt is statistically significant but of doubtful clinical importance

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

The answer and the reasoning

D. It is statistically significant but of doubtful clinical importance

With a very large sample, even a trivial difference can reach a small p value. The p value shows that chance is an unlikely explanation but says nothing about the size or importance of the effect. A 0.5 mmHg reduction is unlikely to matter clinically, so effect size and confidence interval should be considered.

Option by option

A. It shows that the drug lacks any biological effect
A significant difference suggests an effect, although a small one.
B. It is clinically important because the p value is very small
A small p value does not measure how large or important the effect is.
C. It is neither statistically nor clinically significant
The difference is statistically significant, as the p value is below the usual threshold.
D. It is statistically significant but of doubtful clinical importance (correct)
Correct. Large samples can make a tiny effect statistically significant without clinical importance.

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 D, It is statistically significant but of doubtful clinical importance. With a very large sample, even a trivial difference can reach a small p value.

Why is "It shows that the drug lacks any biological effect" not the answer?

A significant difference suggests an effect, although a small one.

Why is "It is clinically important because the p value is very small" not the answer?

A small p value does not measure how large or important the effect is.

Why is "It is neither statistically nor clinically significant" not the answer?

The difference is statistically significant, as the p value is below the usual threshold.

What concept does this question test?

It tests Biostatistics: statistical versus clinical significance in PSM. The p value shows that chance is an unlikely explanation but says nothing about the size or importance of the effect. A 0.5 mmHg reduction is unlikely to matter clinically, so effect size and confidence interval should be considered.

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 Biostatistics: statistical versus clinical significance?

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.