Bias: 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 · Bias

Sample item

What is selection bias?

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

The answer and the reasoning

B. Systematic difference from how participants enter or remain in study

Selection bias occurs when inclusion, retention, or comparison groups are related to exposure and outcome, producing a nonrepresentative association.

Option by option

  • A. Random sampling variation

    Random variation is chance error.

  • B. Systematic difference from how participants enter or remain in study (correct)

    Correct: recruitment or retention can distort association.

  • C. Incorrect data transcription only

    Transcription error is data quality issue.

  • D. Laboratory machine imprecision

    Imprecision is measurement issue.

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 B, Systematic difference from how participants enter or remain in study. Selection bias occurs when inclusion, retention, or comparison groups are related to exposure and outcome, producing a nonrepresentative association.

Why is "Random sampling variation" not the answer?

Random variation is chance error.

Why is "Incorrect data transcription only" not the answer?

Transcription error is data quality issue.

Why is "Laboratory machine imprecision" not the answer?

Imprecision is measurement issue.

What concept does this question test?

It tests Bias in PSM. The correct option holds because: Correct: recruitment or retention can distort association.

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 Bias?

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.