LEARN · EXPLAIN · REVISE

For observations k,k+2,k+4, find variance using denominator 3 as specified.

Read the idea, work independently, then explain what changed.

TOPIC 01

Statistics: mixed assessment

A mixed assessment: identify the method, justify it and revise your reasoning.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Foundation#Your turn

k=8

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Translate counts into sample proportions and keep classes, units and uncertainty visible.

Hint 2

Center the data before squaring; use the stated denominator.

Worked solution

Translate counts into sample proportions and keep classes, units and uncertainty visible.
Calculate or simplify this relation.
$v=[(-2)^2+0^2+2^2]/3=8/3$
This descriptive variance differs from an unbiased sample variance using n−1.

The requested value is 2.66666667.

Checks and common pitfalls: This descriptive variance differs from an unbiased sample variance using n−1.

Think first. Reveal a hint when the class is ready.

Teacher preparation and assessment