Biostatistics: 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

Sample item

A set of hospital stay durations has a few very long stays, giving a distribution with a long tail to the right. Which relationship among the measures of central tendency is expected?

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

The answer and the reasoning

C. Mean greater than median, which is greater than mode

In a positively skewed distribution, the tail of extreme high values pulls the mean upwards more than the median, and the mode lies at the peak. The usual order is mode, then median, then mean.

Option by option

  • A. Mean less than median, which is less than mode

    This order is seen in a negatively skewed distribution with a left tail.

  • B. Median greater than mean, which is greater than mode

    This order does not describe either direction of skew.

  • C. Mean greater than median, which is greater than mode (correct)

    Correct. Extreme high values raise the mean most, with the mode at the peak.

  • D. Mean, median and mode all equal

    All three are equal only in a symmetric distribution such as the normal curve.

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.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is C, Mean greater than median, which is greater than mode. In a positively skewed distribution, the tail of extreme high values pulls the mean upwards more than the median, and the mode lies at the peak.

Why is "Mean less than median, which is less than mode" not the answer?

This order is seen in a negatively skewed distribution with a left tail.

Why is "Median greater than mean, which is greater than mode" not the answer?

This order does not describe either direction of skew.

Why is "Mean, median and mode all equal" not the answer?

All three are equal only in a symmetric distribution such as the normal curve.

What concept does this question test?

It tests Biostatistics in PSM. The usual order is mode, then median, then mean.

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?

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.