Calculator
Values4
Mean7.5
Method and variables
Arithmetic Mean Calculator
Formula: mean = sum of values / number of values
Assumption: Each value is treated with equal weight.
Worked example
Arithmetic Mean Calculator
The mean of 4, 7, 9 and 10 is 30 / 4 = 7.5.
Mean, median and weighted mean
Take the monthly incomes 2,100, 2,300, 2,400, 2,600 and 9,600. The arithmetic mean is 19,000 / 5 = 3,800, but four of the five values are below it. The median, the middle value once sorted, is 2,400 and describes the typical value better. When one or two extreme values pull the mean away from the rest, report the median alongside it.
| Measure | How it is found | Value for the example |
|---|---|---|
| Arithmetic mean | sum / count | 3,800 |
| Median | middle value after sorting | 2,400 |
| Mean without the outlier | 9,400 / 4 | 2,350 |
A weighted mean is needed when values count differently. Exam marks of 70 (weight 30%) and 85 (weight 70%) average to 70 × 0.3 + 85 × 0.7 = 80.5, not the simple mean of 77.5.