condition mean min max ZT0-3 16.978075 16.8212 17.13495 ZT4-7 22.18535 22.18535 22.18535 ZT8-11 18.10495 18.10495 18.10495 ZT12-15 0 0 0 ZT16-19 20.860349999999997 20.860349999999997 20.860349999999997 ZT20-23 20.0585 20.0585 20.0585