Left panel: Distributions of flux ratio of [O III]λ5007 Å to narrow Hα for the AGN (histogram filled with red lines), the HII galaxies (histogram filled with dark green lines), and all the narrow emission line galaxies (histogram filled with blue lines). Middle panel and right panel: Determined distributions of the Spearman rank correlation coefficient, after accepting the uniform distributions (with 1 as the mean value and [0.1, 10] as the minimum and maximum values) and the Gaussian distributions (with 1 as the mean value and 0.5 as the second moment) for the peak intensity ratios.