condition mean min max ZT0-3 7.800000000000001 7.800000000000001 7.800000000000001 ZT4-7 6.9 6.9 6.9 ZT8-11 14.6 14.6 14.6 ZT12-15 6.85 6.85 6.85 ZT16-19 7.65 7.65 7.65 ZT20-23 7.8500000000000005 7.8500000000000005 7.8500000000000005