Classification frequencies of composite spectrum (derived from combining AGN and passive spectra, with respect to the classes considered in our diagnostic scheme) as a function of AGN fractional contribution to the total nuclear (3″) continuum in the SDSS g band. We observe a transition from passive to LINER and then to AGN galaxy classification when the AGN contribution to the nuclear flux in the SDSS g band reaches approximately 10% and 25%, respectively, indicating that our diagnostic is sensitive to AGN contributions in passive galaxies as low as 10% in the g band. The curves depict the average predictions of each class for 20 randomly generated composite spectra, while the shaded areas represent the standard deviation of the classification frequencies.