condition mean min max ZT0-3 7.976156 7.976156 7.976156 ZT4-7 8.4213305 8.4213305 8.4213305 ZT8-11 7.806104 7.806104 7.806104 ZT12-15 7.527204 7.527204 7.527204 ZT16-19 7.7504615 7.7504615 7.7504615 ZT20-23 8.370489 8.370489 8.370489