The square root of the variance is called as

Variance is the average of the squared deviations of each observation from the mean of a data set, and it is expressed in squared units of the original data. Taking the positive square root of the variance converts this measure back into the original unit, and this square root of the variance is, by definition, called the standard deviation (denoted σ, so σ = √Variance).

The question describes exactly this relationship — the square root of the variance — which matches the definition of standard deviation, so ‘Standard deviation’ is the term being asked for.

• Mean deviation aggregates absolute (not squared) deviations from the mean or median, so it is not obtained by taking a square root of the variance.

• Coefficient of variation is a further ratio of the standard deviation to the mean (usually expressed as a percentage), a derived relative measure rather than the square root of variance itself.

• Mode is a measure of central tendency (the most frequent value), unrelated to how spread is measured.

Hence, the square root of the variance is standard deviation.