condition mean min max ZT0-3 7.505526666666667 7.042870000000001 8.340665000000001 ZT4-7 5.2759 5.2759 5.2759 ZT8-11 4.65227 4.65227 4.65227 ZT12-15 6.690785 6.631125 6.750445000000001 ZT16-19 7.22989 7.22989 7.22989 ZT20-23 7.417185 7.417185 7.417185