condition mean min max ZT0-3 7.820455 7.820455 7.820455 ZT4-7 8.772392 8.772392 8.772392 ZT8-11 7.9775624999999994 7.9775624999999994 7.9775624999999994 ZT12-15 8.2451975 8.2451975 8.2451975 ZT16-19 9.345762 9.345762 9.345762 ZT20-23 8.157695499999999 8.157695499999999 8.157695499999999