Inverse Gaussian distribution

The probability density function for the inverse Gaussian distribution is:

.. math::

f(x, k) = \frac{1}{\sqrt{2 \pi x^3}}
                \exp(-\frac{(x-k)^2}{2 x k^2})

where :math:x \ge 0, k > 0. The following plots show the pdf and cdf:

.. image:: ../../../../tests/imgs/stats/continuous/invgauss/invgausspdf.png :align: center :width: 480

.. image:: ../../../../tests/imgs/stats/continuous/invgauss/invgausscdf.png :align: center :width: 480