Computes the probability that a Gaussian distribution lies
    within a range of values.

    Parameters
    ----------

    x_range : (float, float)
        tuple of range to compute probability for

    mu : float
        mean of the Gaussian

    var : float, optional
        variance of the Gaussian. Ignored if `std` is provided

    std : float, optional
       standard deviation of the Gaussian. This overrides the `var` parameter

    Returns
    -------

    probability : float
        probability that Gaussian is within x_range. E.g. .1 means 10%.

def norm_cdf(x_range, mu, var=1, std=None):
    """
    Computes the probability that a Gaussian distribution lies
    within a range of values.

    Parameters
    ----------

    x_range : (float, float)
        tuple of range to compute probability for

    mu : float
        mean of the Gaussian

    var : float, optional
        variance of the Gaussian. Ignored if `std` is provided

    std : float, optional
       standard deviation of the Gaussian. This overrides the `var` parameter

    Returns
    -------

    probability : float
        probability that Gaussian is within x_range. E.g. .1 means 10%.
    """

    if std is None:
        std = math.sqrt(var)
    return abs(norm.cdf(x_range[0], loc=mu, scale=std) -
               norm.cdf(x_range[1], loc=mu, scale=std))