Exploring data: graphs and numerical summaries

# 5.8 Sample variance

It is worth noting that a special term is reserved for the square of the sample standard deviation: it is known as the sample variance.

## The sample variance

The sample variance of a data sample x 1, x 2, …, xn is given by

where is the sample mean.

## Example 3: Calculating the variance

The variance of the eleven β endorphin concentration differences is

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