Understand the subject
What is a weighted average?
A weighted average is an average in which some values count more than others. Each value is paired with a non-negative weight representing its frequency, share, credits, exposure, or agreed importance.
It is useful when groups have different sizes or contributions. An ordinary mean would wrongly treat every row as equally influential.
The relationship
Weighted-average formula
xᵢ is a value, wᵢ is its matching weight, and wᵢxᵢ is that row’s contribution to the weighted total.
See the influence
A larger weight repeats a value’s influence
The score 90 occupies three of the four total weight units, so the result sits closer to 90 than to 80.
Worked example
Scores with unequal weights
Pair 80 with weight 1 and 90 with weight 3. First form the weighted total, then divide by total weight.
(80×1 + 90×3) ÷ (1+3) = 350 ÷ 4 = 87.5
Interpret with care
Weights need a real meaning
Weights need not add to 1 or 100—the calculator normalizes them—but they must use one consistent meaning. A zero-weight row has no effect. Do not average already-averaged groups equally when their group sizes differ; use those sizes as weights.