'ttests for no-interaction terms are zero'

def ttest_interaction(self):

    nia = self.n_interaction
    R_nointer = np.hstack((np.zeros((nia, (self.nvars - nia))), np.eye(nia)))
    R_nointer_transf = self.transform.inv_dot_right(R_nointer)
    self.R_nointer_transf = R_nointer_transf
    t_res = self.resols.t_test(R_nointer_transf)
    return t_res
