Choosing the best average
The Maths Habit
Find the mean of 8, 3, 11, 6, 7
7Find the median of 15, 9, 22, 12, 18, 30
16.5Find the mode and the range of 4.5, 6, 3.5, 6, 8, 5
mode 6, range 4.5
What is the mean number of legs for a person in the UK?
Just under 2
- Outlier
- A value that is much bigger or much smaller than the rest of the data.
An outlier: use the median
No outlier: use the mean
Words, not numbers: use the mode
Marks for 7 students. Which average describes the group better?
Pay (£ per hour) for 7 workers.
Which average describes the group better?
Goals for 7 players.
Which average describes the group better?
Pay (£ per hour) for 7 workers.
Which average describes the group better?
Times (seconds) for 7 runners.
Which average describes the group better?
Pay (£ per hour) for 7 workers.
Which average describes the group better?
Marks out of 20 for 7 students.
Which average describes the group better?
Pay (£ per hour) for 7 workers.
Which average describes the group better?
Heights (cm) of 6 plants.
Which average describes the group better?
Pay (£ per hour) for 7 workers.
Which average describes the group better?
Texts sent in a day by 5 friends.
Which average describes the group better?
Favourite fruit in a class. Which average can describe this group?
Answer sheet
A company says its average pay is £52 000. Six staff earn £30 000 each and the owner earns £184 000. Which average has the company used? Is it a fair one?
The mean. No: the owner is an outlierAlmost everyone has 2 legs. A few people have fewer. Why is the mean number of legs less than 2?
The few low values pull the mean down
Find the mean and the median of 4, 1, 26, 5, 3, 6, 4
mean 7, median 4Which average describes the data in question 1 better? Give a reason.
Median: 26 is an outlierPets in a class: cat, dog, fish, dog, hamster, dog, cat. Which average can be used? Find it.
The mode: dog