condition mean min max ZT0-3 7.35 7.35 7.35 ZT4-7 3.5 3.5 3.5 ZT8-11 12.5 12.5 12.5 ZT12-15 23.45 23.45 23.45 ZT16-19 7.300000000000001 7.300000000000001 7.300000000000001 ZT20-23 8.8 8.8 8.8