Corner plots showing the distributions and mutual relations of skewness and entropy of redshift PDFs for well-classified (blue) and poorly classified (red) galaxy spectra. The threshold for a good prediction is set at |Δz|< 0.01. Top panel: Results for spectra with an exposure time of t_exp = 2 h. Bottom panel: Results for spectra with t_exp = 8 h. Well-classified spectra and poorly classified spectra are clearly distinguished by their skewness and entropy values (see a discussion in Sect. 5). The vertical orange lines indicate the separation threshold for skewness = 20 and entropy = 2.