The statistical distribution and correlation relationship of the empirical neutron-proton (np) interaction are analyzed, whereby the interaction strengths are extracted from the binding energies using a known four-point formula. By comparing the correlations of the data and those from numerical simulations of the random number method, it is shown that an additional attractive np interaction persists between the last proton and last neutron in odd-odd nuclei. It provides evidence of the residual np interaction from statistical analysis. The adopted new analytical method might be a useful way to clarify the inherent correlation.