Dependence between some spectral and physical characteristics of quasars

Using 192 composite spectra stacked from subsamples of individual SDSS DR7 quasar spectra binned in spectral index, $\alpha_{\lambda}$, and logarithm of monochromatic luminosity at 1450 \AA, $\log{l_{1450}}$, we found that there is a dependence of the emission line equivalent width (EW) on spectral index (correlation or anti-correlation) for some lines, mostly for those lines for which the Baldwin effect is detected. We also show that there is no dependence between the virial mass of the central supermassive black hole of a quasar and its spectral index $\alpha_{\lambda}$.