condition mean min max ZT0-3 3.787465 3.787465 3.787465 ZT4-7 2.481985 2.481985 2.481985 ZT8-11 3.19772 3.19772 3.19772 ZT12-15 2.39965 2.39965 2.39965 ZT16-19 5.02529 5.02529 5.02529 ZT20-23 3.709355 3.709355 3.709355