Measures of Dispersion summary

Key learning points

• Range = max − min (outlier-sensitive).
• IQR = Q3 − Q1 (more robust).
• Standard deviation is the square root of variance.
• Compare distributions using both location and spread.

Worked example 1 — From variance

Variance is 9. Standard deviation?

Working

s.d. = $\sqrt{\text{variance}}$.

Worked example 2 — Range = max − min (outlier-sensitive)

Use this method from the Measures of Dispersion sheet: Range = max − min (outlier-sensitive).

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 3 — IQR = Q3 − Q1 (more robust)

Use this method from the Measures of Dispersion sheet: IQR = Q3 − Q1 (more robust).

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 4 — Standard deviation is the square root of variance

Use this method from the Measures of Dispersion sheet: Standard deviation is the square root of variance.

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 5 — Compare distributions using both location and spread

Use this method from the Measures of Dispersion sheet: Compare distributions using both location and spread.

Working

Each key learning point matches a question type on the printable worksheet.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.