Standard deviation

\sigma=\sqrt{\sigma^2}

Result unit: — (jednostki danych)

What it describes

The square root of the variance — the spread of the data in the same units as the data.

\sigma

standard deviation

\sigma^2

variance

The square root of the variance — it brings the spread back to the same units as the data, making it easier to interpret.

The typical measure of data dispersion (spread of results, risk).

The variance is

\sigma^2=9

. Find the standard deviation.

Substitution

\sigma^2=9

Result

\sigma=\sqrt9=3

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