condition mean min max ZT0-3 6.8 6.8 6.8 ZT4-7 7.5 7.5 7.5 ZT8-11 3.85 3.85 3.85 ZT12-15 7.1499999999999995 7.1499999999999995 7.1499999999999995 ZT16-19 11.45 11.45 11.45 ZT20-23 9.3 9.3 9.3