
{{alias}}( r, p )
    Returns the standard deviation of a negative binomial distribution.

    If provided `NaN` as any argument, the function returns `NaN`.

    If provided a `r` which is not a positive number, the function returns
    `NaN`.

    If provided a success probability `p` outside of `[0,1]`, the function
    returns `NaN`.

    Parameters
    ----------
    r: integer
        Number of failures until experiment is stopped.

    p: number
        Success probability.

    Returns
    -------
    out: number
        Standard deviation.

    Examples
    --------
    > var v = {{alias}}( 100, 0.2 )
    ~44.721
    > v = {{alias}}( 20, 0.5 )
    ~6.325

    See Also
    --------

