Bias: confounding: 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.

Try it

PSM · Bias: confounding

Sample item

Coffee drinking appears associated with lung cancer, but smoking is more common among coffee drinkers and independently causes lung cancer. Smoking is acting as what?

AA confounderBA diagnostic gold standardCAn effect modifier by definitionDA random error

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

The answer and the reasoning

A. A confounder

A confounder is associated with the exposure and independently affects the outcome, while not lying on the causal pathway. Smoking can distort an apparent coffee-lung cancer association.

Option by option

A. A confounder (correct)
Correct. Smoking meets the classic confounding conditions in this example.
B. A diagnostic gold standard
A gold standard is a reference diagnostic method.
C. An effect modifier by definition
Effect modification is a real difference in effect across strata, not automatically present here.
D. A random error
Random error is due to chance variation.

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 A, A confounder. A confounder is associated with the exposure and independently affects the outcome, while not lying on the causal pathway.

Why is "A diagnostic gold standard" not the answer?

A gold standard is a reference diagnostic method.

Why is "An effect modifier by definition" not the answer?

Effect modification is a real difference in effect across strata, not automatically present here.

Why is "A random error" not the answer?

Random error is due to chance variation.

What concept does this question test?

It tests Bias: confounding in PSM. Smoking can distort an apparent coffee-lung cancer 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: confounding?

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.