Range (Edexcel IGCSE Maths)

Spec point — 4D

Range

What is the range of a data set?

• The range is the difference between the highest value and the lowest value

  • range = highest - lowest

    • For example, the range of 1, 2, 5, 8 is 8 - 1 = 7

• It measures how spread out the data is

  • Ranges of different data sets can be compared to see which is more spread out
  • The range of a data set can be affected by very large or small values

• Be careful with negatives

  • The range of -2, -1, 0, 4 is 4 - (-2) = 6

• The range is a simple measure of how spread out the data is

  • The range does not measure an average value

Exam Hint If asked to find the range in an exam, make sure you show your subtraction clearly (don't just write down the answer).

Worked Example Here are four numbers written in order of size.

$w9x22$

The range of the four numbers is 19.

Find the value of $w$.

Answer:

The range is the largest value minus the smallest value

Set up an equation and solve for $w$

$\begin{gathered} 19 = 22 - w \\ w = 22 - 19 \\ w = 3 \end{gathered}$

$w=3$

Worked Example Find the range of the data in the table below.

3.4	4.2	2.8	3.6	9.2	3.1	2.9	3.4	3.2
3.5	3.7	3.6	3.2	3.1	2.9	4.1	3.6	3.8
3.4	3.2	4.0	3.7	3.6	2.8	3.9	3.1	3.0

Answer:

Range = highest value - lowest value

9.2 - 2.8

Final answer: The range is 6.4