Core-collapse supernova explosions expose the structure and environment of massive stars at the moment of their death. We use the global fitting technique of Pejcha & Prieto (2015a,b) to derive a set of physical parameters of normal Type II SNe, such as their distance moduli, reddenings, $^{56}$Ni masses $M_{\rm Ni}$, and explosion energies $E_{\rm exp}$ from multicolor light curves and photospheric velocities. We confirm and characterize known correlations between $M_{\rm Ni}$ and bolometric luminosity at 50 days after the explosion, and between $M_{\rm Ni}$ and $E_{\rm exp}$. We pay special attention to the observed distribution of $M_{\rm Ni}$, which can be described as a skewed-Gaussian-like distribution between $0.005~M_{⊙}$ and $0.280~M_{⊙}$, with a median of $0.031~M_{⊙}$, mean of $0.045~M_{⊙}$, standard deviation of $0.049~M_{⊙}$ and skewness of $3.188$. We use two-sample KS test to compare the observed distribution of $M_{\rm Ni}$ to results from theoretical hydrodynamical codes of core-collapse explosions with the neutrino mechanism presented in the literature. Our results show that the distributions coming from the KEPLER code match the observations better and are not sensitive to different pre-supernova calibrations and the different constrains on the progenitors initial mass function. ; Comment: submitted to ApJ