condition mean min max ZT0-3 7.965899 7.965899 7.965899 ZT4-7 7.684381999999999 7.684381999999999 7.684381999999999 ZT8-11 7.9959585 7.9959585 7.9959585 ZT12-15 7.255999 7.255999 7.255999 ZT16-19 7.4124255 7.4124255 7.4124255 ZT20-23 7.16657 7.16657 7.16657