The range — Data, 7–10 years
The range shows how far apart the smallest and largest values in a data set are. Data, 7–10 years.
From smallest to largest
The range describes the width of a set of numbers. Find the largest value and the smallest value, then work out how far apart they are by subtracting. A small range means the results are close together; a large range means they are more spread out.
Why measure the range?
Two groups can have the same average but feel very different: in one, everyone may be close to the average, while in the other, results may be far apart. The range gives a quick answer about spread. It solves the problem of a single average hiding how much the results vary.
Calculating a range
A plant grows 3, 5, 6 and 10 centimetres in four weeks. The smallest measurement is 3 cm and the largest is 10 cm. Subtract: 10 − 3 = 7. The range is 7 centimetres, so the measurements stretch across seven centimetres from the smallest to the largest.
Do not add the ends
When people see two important end values, they may add them because adding often combines amounts. But range asks for the distance between the ends, so we subtract the smallest from the largest. For 4 and 11, the range is 11 − 4 = 7, not 15.
Range outside school
A gardener can use the range of daily temperatures to see how much the weather changed during a week. A coach can compare the range of race times to see whether runners finished close together or far apart. The range is a quick guide, not a description of every result.
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