Types of averages
The arithmetic mean
The arithmetic mean is the most widely used average. It is calculated by summing all values and dividing by the count. For example, given the grades 12, 15, 8 and 17, the mean is (12 + 15 + 8 + 17) / 4 = 13. This is the standard method for computing grade averages, weekly temperature averages or mean satisfaction scores from a survey.
When to use it
The arithmetic mean works well when data is distributed fairly evenly. It is suitable for comparing student performance, tracking daily temperature changes or summarising poll responses on à 1-to-10 scale.
Watch out for outliers
The main weakness of the arithmetic mean is its sensitivity to extreme values. In a group of five salariés (2,000, 2,200, 2,100, 2,300, 15,000), the mean reaches 4,720 EUR, a figure that represents none of the actual salariés. In such cases, the median (2,200 EUR) paints a far more accurate picture of the typical situation. This is why income statistics often report the median rather than the mean.