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# Weighted Mean

The weighted mean, or the weighted average, of a numerical data set is a type of mean that is used when some data values are weighted more than others. Mathematically, it is the sum of the product of weights and associated data values divided by the summation of weights for data.

As an example, think three point assignments that are worth different percentages of the total grade of a course as shown in the table with the scores of a student.

Assignments Scores Weights
Exam
Quiz
Term Paper
Decimal forms of the percentages are used in the formula.
If the weights are equal —no matter what value —, then the weighted mean equals the arithmetic mean.