Surface electron ejection by laser excited metastable (SEELEM) and laser induced fluorescence (LIF) spectroscopies are complementary techniques that can be employed to provide both qualitative and quantitative insights into the mechanisms of singlet-triplet coupling in small polyatomic molecules. Two qualitatively distinct singlet-triplet coupling mechanisms are examined here in order to reveal the statistical signatures by which they can best be distinguished. These interaction mechanisms are: direct coupling between a "bright" S-1 state and an entire background manifold of "dark" triplet states; and "doorway-mediated" indirect coupling in which the bright state couples to the manifold of dark states through the intermediary of one doorway state of unique vibronic character. Our goal in this paper is to present and explain the basis for the effectiveness of statistical methods with which complex LIF/SEELEM spectra may be processed so as to distinguish qualitatively between these two mechanistic possibilities. The trends obtained from these statistical methods are also shown to encode information about some characteristic quantitative features of the triplet perturbers, such as their coupling strength to the bright state S-1. The development of the statistical methods described in this paper was motivated by our experiments on acetylene. Acetylene has certain useful dynamical features which make it a good model system for this study. The statistical measures developed distinguish conclusively between the direct and doorway-mediated coupling schemes, because each scheme is shown here to give rise to characteristic statistical signatures in the SEELEM and LIF spectra. Qualitative results from a preliminary real data set analyzed using the statistical approach proposed here are also presented in order to demonstrate the effectiveness of these statistical measures.