Data Handling
Primary 6 · Mathematics
Data Handling
Lesson 2 of 4
20 min
Let's begin
Keza's marks in seven weekly spelling tests, each out of 20, were 12, 15, 9, 15, 18, 14 and 8. Her mother asks: "So, how are you doing?"
Keza could read out all seven marks, but one number that sums them up would be better. In this lesson you will meet four such numbers: the mean, the median, the mode and the range.
Imagine pouring all of Keza's marks into one pot and sharing them out equally between the 7 tests. Each test's fair share is the mean (also called the average).
mean = sum of the values ÷ number of values
Want to see the fair share happen? Try the Mean: Share and Balance simulation: level out the water in the cups, or share out the chocolate bars, and watch the mean appear.
Sort the values from smallest to largest. The median is the one in the middle.
Keza's marks sorted: 8, 9, 12, 14, 15, 15, 18. There are 7 values, so the middle one is the 4th: the median is 14.
If there is an even number of values, there are two middle values, and the median is halfway between them.
Worked example 1
the heights of six pupils are 140, 146, 138, 150, 142 and 148 cm. Sorted: 138, 140, 142, 146, 148, 150. Median = (142 + 146) ÷ 2 = 288 ÷ 2 = 144 cm.
The mode is the value that appears most often. In Keza's marks, 15 appears twice and every other mark once, so the mode is 15. If no value repeats, there is no mode; if two values tie for most often, both are modes.
range = highest value − lowest value. For Keza: 18 − 8 = 10. A small range means the values are close together; a large range means they are spread out.
Worked example 2
the table shows how many people live in each of 20 households in an umudugudu.
| People in the household | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|
| Number of households (frequency) | 3 | 5 | 6 | 4 | 2 |
Tip
Mean = share it out fairly. Median = the middle, after sorting. MOde = the MOst common. Range = biggest minus smallest.
Answers
What you learned today
Sources and credits
The spelling-test and umudugudu examples were written by Ganzaa.
Quick check
Five test marks are 12, 7, 15, 7 and 9. Match each word to its value.
Tap one on the left, then its partner on the right.
