Math & Statistics

What Is the Mean?

The mean, or arithmetic average, is the sum of all values in a data set divided by the number of values. For 2, 4, and 9, the mean is (2 + 4 + 9) ÷ 3 = 5. It is the most common measure of a data set's center.

Formula

Mean = (x₁ + x₂ + … + xₙ) ÷ n.

Mean vs. Median

The mean is sensitive to outliers: a single very large value can pull it far from the typical value. In skewed data, such as incomes, the median is often a better indicator of the typical case.

Other Averages

A weighted mean gives some values more influence than others, as in a grade point average, and a geometric mean is used for growth rates.

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🔗 Related Terms

Median Mode Standard Deviation

More Math & Statistics Terms

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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.