condition mean min max ZT0-3 7.252192 7.252192 7.252192 ZT4-7 7.232365 7.232365 7.232365 ZT8-11 8.2998935 8.2998935 8.2998935 ZT12-15 7.600524999999999 7.600524999999999 7.600524999999999 ZT16-19 7.692526 7.692526 7.692526 ZT20-23 8.2545715 8.2545715 8.2545715