> ## Documentation Index
> Fetch the complete documentation index at: https://docs.activeviam.com/llms.txt
> Use this file to discover all available pages before exploring further.

# atoti.array.var()

### atoti.array.var(measure, /, \*, mode='sample')

Return a measure equal to the variance of the elements of the passed array measure.

* **Parameters:**
  * **measure** (*VariableMeasureConvertible*) – The measure to get the variance of.
  * **mode** ([*Literal*](https://docs.python.org/3/library/typing.html#typing.Literal) *\[* *'sample'* *,*  *'population'* *]*) –

    One of the supported modes:

    * The `sample` variance, similar to Excel’s `VAR.S`, is $\frac{\sum_{i=1}^{n} (X_i - m)^{2}}{n - 1}$ where `m` is the sample mean and `n` the size of the sample.
      Use this mode if the data represents a sample of the population.
    * The `population` variance, similar to Excel’s `VAR.P` is $\frac{\sum_{i=1}^{n}(X_i - m)^{2}}{n}$ where `m` is the mean of the `Xi` elements and `n` the size of the population.
      Use this mode if the data represents the entire population.
* **Return type:**
  *MeasureDefinition*