Find the range of 12, 8, 15, 21.

13

Range = Highest value − Lowest value = 21 − 8 = 13.

Understanding Statistics questions

Statistics questions ask you to summarise a data set with a single representative figure or a measure of spread. The arithmetic is light; picking the right measure is the real skill.

How to approach it

1. Order the data when median or range is involved.
2. Use mean = sum ÷ number of values, median = middle value, mode = most frequent value.
3. For grouped data, use class midpoints as representative values.
4. State the answer with the same units as the original data.

Common mistakes to avoid

• Forgetting to sort the values before finding the median.
• Including the frequency column in the sum instead of the values.
• Assuming a data set has exactly one mode.

Where it appears: Covered in CBSE Class 9–12, IGCSE, and IB Applications and Interpretation.