condition mean min max ZT0-3 8.450331 8.450331 8.450331 ZT4-7 8.7577585 8.7577585 8.7577585 ZT8-11 7.451582500000001 7.451582500000001 7.451582500000001 ZT12-15 9.0705815 9.0705815 9.0705815 ZT16-19 8.5833435 8.5833435 8.5833435 ZT20-23 8.203145500000002 8.203145500000002 8.203145500000002