condition mean min max ZT0-3 7.667475 7.667475 7.667475 ZT4-7 4.589365 4.589365 4.589365 ZT8-11 6.770115 6.770115 6.770115 ZT12-15 5.804855 5.804855 5.804855 ZT16-19 9.327055 9.327055 9.327055 ZT20-23 8.10658 8.10658 8.10658