> ## 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.

# ppf()

<span id="atoti.stats.normal.ppf" />

> atoti.stats.normal.ppf(<br />
>     *point*: VariableMeasureConvertible,<br />
>     /,<br />
>     \*,<br />
>     *mean*: NumericMeasureConvertible,<br />
>     *standard\_deviation*: StrictlyPositiveNumber | VariableMeasureConvertible,<br />
> ) → MeasureDefinition

Percent point function for a normal distribution.

<Warning>
  This feature is [`experimental`](./atoti.experimental#atoti.experimental), its key is `"stats.normal.ppf"`.
</Warning>

Also called inverse cumulative distribution function.

The ppf is given by the formula

$$
\operatorname {{ppf}}(x) = \mu + \sigma \sqrt{{2}} \operatorname {{erf}} ^{{-1}}(2x-1)
$$

Where $\mu$ is the mean of the distribution, $\sigma$ is its standard deviation and $\operatorname {{erf}}^{{-1}}$ the inverse of the error function.

### Parameters

<h4 id="atoti.stats.normal.ppf.point">
  *point*
</h4>

The point where the function is evaluated.

<h4 id="atoti.stats.normal.ppf.mean">
  *mean*
</h4>

The mean value of the distribution.

<h4 id="atoti.stats.normal.ppf.standard_deviation">
  *standard\_deviation*
</h4>

The standard deviation of the distribution.
Must be positive.

***

<Callout icon="link">
  **See also**:
  [Quantile function of a normal distribution](https://en.wikipedia.org/wiki/Normal_distribution#Quantile_function).
</Callout>