Averages and grades: mean, median and weighted averages

Mean and median

• Mean — add everything and divide by how many there are.
• Median — the middle value when the numbers are sorted. It isn't pulled around by a few very large or small values, which is why incomes and house prices are often reported as medians.

Weighted average

When items count differently, multiply each by its weight, add the results, and divide by the total weight. University grade averages work this way, weighted by course units.

Worked example (0–20 scale)

• A 3-unit course with a grade of 17
• A 2-unit course with a grade of 15
• A 4-unit course with a grade of 18

Weighted average: (3 × 17 + 2 × 15 + 4 × 18) ÷ (3 + 2 + 4) = 153 ÷ 9 = 17.00.

The simple mean of the three grades would be 16.67 — lower, because it gives the small 2-unit course the same weight as the large 4-unit one.

Tip

To see how much a future grade can raise your average, add it with its units to the running totals and divide again.

Tools for this

• Education cost estimator