def informedness(self):
return self.recall() + self.specificity() - <NUM_LIT:1><EOL>
Return informedness.

        Informedness is defined as :math:`sensitivity + specificity - 1`.

        AKA Youden's J statistic (:cite:`Youden:1950`)

        AKA DeltaP'

        Cf. https://en.wikipedia.org/wiki/Youden%27s_J_statistic

        Returns
        -------
        float
            The informedness of the confusion table

        Example
        -------
        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.informedness()
        0.55