condition mean min max ZT0-3 2.0362133333333334 0.94459 2.644235 ZT4-7 1.7807 1.7807 1.7807 ZT8-11 1.8456099999999998 1.8456099999999998 1.8456099999999998 ZT12-15 2.7109525000000003 2.40085 3.021055 ZT16-19 2.71402 2.71402 2.71402 ZT20-23 2.8679 2.8679 2.8679