condition mean min max ZT0-3 3.589881666666667 3.23102 3.8788300000000002 ZT4-7 3.0315149999999997 3.0315149999999997 3.0315149999999997 ZT8-11 4.865715 4.865715 4.865715 ZT12-15 6.594952500000001 5.120955 8.068950000000001 ZT16-19 5.56667 5.56667 5.56667 ZT20-23 5.79893 5.79893 5.79893