condition mean min max ZT0-3 18.7 18.7 18.7 ZT4-7 9.5 9.5 9.5 ZT8-11 11.75 11.75 11.75 ZT12-15 19.799999999999997 19.799999999999997 19.799999999999997 ZT16-19 20.05 20.05 20.05 ZT20-23 40.25 40.25 40.25