condition mean min max ZT0-3 7.473939 7.473939 7.473939 ZT4-7 7.89831 7.89831 7.89831 ZT8-11 8.145279 8.145279 8.145279 ZT12-15 7.775373 7.775373 7.775373 ZT16-19 8.01965 8.01965 8.01965 ZT20-23 9.5204915 9.5204915 9.5204915