Range
What is range of a set of data?
- The three averages (mean, median and mode) measure what is called central tendency
- they all give an indication of what is typical about the data
- what lies roughly in the middle
- The range measures how spread out the data is
- This can only be applied to numerical data
How do I work out the range?
- The range is the difference between the highest data value and the lowest data value
- It measures how spread out the data is
- You can remember this as "Hi - Lo"
- There is one possible problem with the range
- as it considers the highest and lowest values in the data set it could be influenced by outliers in the data
- these may not be a true representation of how spread the rest of the data may be
Examiner Tip
- Remember with the range that you have to do a calculation (even if it is an easy subtraction)
- it is not enough to write something like the range is 14 to 22
Worked example
Find the range for the following data.
| 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 |
You only need two numbers for the range, the highest and the lowest.
Range = Hi - Lo = 9.2 - 2.8 = 6.4
The range is 6.4
