Averages, made simple.
An average can summarise a collection of numbers. This lesson focuses on the mean: add all the values, then divide by how many values there are. Imagine sharing a total equally. The mean tells you how much each group would receive if every group had the same amount.
Use the mean formula
Mean = sum of values ÷ number of values. For 4, 6 and 8, the sum is 18 and there are 3 values. The mean is 18 ÷ 3 = 6. Keep repeated values when counting.
Count zeros too
Zero is still a value. For 0, 3 and 6, the mean is 9 ÷ 3 = 3. Leaving out the zero would change the data and give a different answer. A missing value is different from a recorded zero.
Keep the units
The mean has the same unit as the original values. If you average distances measured in centimetres, report the result in centimetres. A mean need not be one of the original values or a whole number.
Check what the mean represents
A very large or small value can pull the mean towards it. The mean of 2, 3 and 25 is 10, although none of these values equals 10. Also, do not simply average two group means when the groups contain different numbers of values.
Meera reads 12, 16, 10, 18 and 14 pages over five days. What is her mean number of pages per day?
- Add the pages: 12 + 16 + 10 + 18 + 14 = 70.
- Count the recorded days: 5.
- Divide the total by the count: 70 ÷ 5 = 14.
14 pages per day
Take it with you: Add every recorded value, count them carefully, then divide and include the unit.