public void ValidateInverseCumulativeDistribution(double dof, double x, double expected)
 {
     var chiSquared = new ChiSquared(dof);
     Assert.That(chiSquared.InverseCumulativeDistribution(x), Is.EqualTo(expected).Within(1e-14));
     Assert.That(ChiSquared.InvCDF(dof, x), Is.EqualTo(expected).Within(1e-14));
 }