Biostatistics: class interval: 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 · Biostatistics: class interval

Sample item

Ages of participants range from 12 to 92 years and are to be grouped into 8 classes of equal width. What approximate class interval should be used?

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

The answer and the reasoning

B. 10 years

The class width is roughly the range divided by the desired number of classes. The range is 92 minus 12, which is 80 years, and 80 divided by 8 gives 10 years. Classes of equal width allow histograms and frequency polygons to be drawn simply.

Option by option

  • A. 12 years

    This is the lowest age and has no link with class width.

  • B. 10 years (correct)

    Correct. A range of 80 years divided by 8 classes gives about 10 years.

  • C. 80 years

    This is the full range, which would give only one class.

  • D. 8 years

    This is the number of classes and not the width.

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, 10 years. The class width is roughly the range divided by the desired number of classes.

Why is "12 years" not the answer?

This is the lowest age and has no link with class width.

Why is "80 years" not the answer?

This is the full range, which would give only one class.

Why is "8 years" not the answer?

This is the number of classes and not the width.

What concept does this question test?

It tests Biostatistics: class interval in PSM. The range is 92 minus 12, which is 80 years, and 80 divided by 8 gives 10 years. Classes of equal width allow histograms and frequency polygons to be drawn simply.

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: class interval?

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.