'rows of the table, linearly interpolated for given sample size
Parameters
n : float
sample size, second parameter of the table
Returns
critv : ndarray, 1d
critical values (ppf) corresponding to a row of the table
Notes
This is used in two step interpolation, or if we want to know the
critical values for all alphas for any sample size that we can obtain
through interpolation'

def _critvals(self, n):

    return np.array([p(n) for p in self.polyn])
