Statistics Dictionary

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Mean

A mean score is an average score, often denoted by X. It is the sum of individual scores divided by the number of individuals. Thus, if you have a set of N numbers ( X1 , X2 , X3 , . . . XN ), the mean of those numbers would be defined as:

X = ( X1 + X2 + X3 + . . . + XN ) / N = [ Σ Xi ] / N

For example, the mean of the numbers 1, 2, and 3 would be (1 + 2 + 3)/3 or 2.

Note: The mean score of a random variable (also called the expected value) is defined somewhat differently. See expected value.

See also:   Statistics Tutorial: Measures of Central Tendency | AP Statistics Tutorial: Measures of Central Tendency