condition mean min max ZT0-3 3.0696183333333336 2.279145 3.8025200000000003 ZT4-7 0.8957885 0.8957885 0.8957885 ZT8-11 1.6798350000000002 1.6798350000000002 1.6798350000000002 ZT12-15 3.1661975 3.1126300000000002 3.2197649999999998 ZT16-19 3.831805 3.831805 3.831805 ZT20-23 4.03782 4.03782 4.03782