condition mean min max ZT0-3 20.265684 20.265684 20.265684 ZT4-7 21.8296545 21.8296545 21.8296545 ZT8-11 20.386062 20.386062 20.386062 ZT12-15 19.59044 19.59044 19.59044 ZT16-19 19.888284499999997 19.888284499999997 19.888284499999997 ZT20-23 18.966423 18.966423 18.966423