  We present an analysis of observed trends and correlations between a large
range of spectral and photometric parameters of more than 100 type II
supernovae (SNe~II), during the photospheric phase. We define a common epoch
for all SNe of 50 days post-explosion where the majority of the sample is
likely to be under similar physical conditions. Several correlation matrices
are produced to search for interesting trends between more than 30 distinct
light-curve and spectral properties that characterize the diversity of SNe~II.
Overall, SNe with higher expansion velocities are brighter, have more rapidly
declining light-curves, shorter plateau durations, and higher $^{56}$Ni masses.
Using a larger sample than previous studies, we argue that `$Pd$' - the plateau
duration from the transition of the initial to `plateau' decline rates to the
end of the `plateau' - is a better indicator of the hydrogen envelope mass than
the traditionally used optically thick phase duration ($OPTd$: explosion epoch
to end of plateau). This argument is supported by the fact that $Pd$ also
correlates with s$_3$, the light-curve decline rate at late times: lower $Pd$
values correlate with larger s$_3$ decline rates. Large s$_3$ decline rates are
likely related to lower envelope masses that enables gamma-ray escape. We also
find a significant anticorrelation between $Pd$ and s$_2$ (the plateau decline
rate), confirming the long standing hypothesis that faster declining SNe~II
(SNe~IIL) are the result of explosions with lower hydrogen envelope masses and
therefore have shorter $Pd$ values.
