  The origin of the luminosity dependence of the strength of broad and narrow
emission lines in AGN (i.e. the Baldwin effect) is not firmly established yet.
We explore this question using the Boroson & Green sample of the 87 z<=0.5 PG
quasars. UV spectra of the C IV region with a sufficient S/N are available for
81 of the objects. We use these spectra to explore the dependence of the C IV
EW on M_BH and L_Edd, as deduced from optical spectra of the H beta region. We
find a strong correlation of the C IV EW with L_Edd. This may be the primary
correlation which drives the Baldwin effect for C IV. A similar correlation
analysis using the C IV FWHM instead of the H beta FWHM, yields an
insignificant correlation. This suggests that the C IV FWHM provides a
significantly less accurate estimate of M_BH compared to the H Beta FWHM. We
also measured the [O III] 4363 /[O III] 5007 line ratio for 72 objects in this
sample, and use it to determine whether density or covering factor control the
large range in [O III] 5007 strength in AGN.
