condition mean min max ZT0-3 2.033515 2.033515 2.033515 ZT4-7 1.8157549999999998 1.8157549999999998 1.8157549999999998 ZT8-11 2.55624 2.55624 2.55624 ZT12-15 3.72731 3.72731 3.72731 ZT16-19 4.229365 4.229365 4.229365 ZT20-23 2.477445 2.477445 2.477445