condition mean min max ZT0-3 21.104275 20.85785 21.3507 ZT4-7 16.5673 16.5673 16.5673 ZT8-11 17.6864 17.6864 17.6864 ZT12-15 0 0 0 ZT16-19 26.36035 26.36035 26.36035 ZT20-23 22.5533 22.5533 22.5533