condition mean min max ZT0-3 6.370416 6.370416 6.370416 ZT4-7 7.733095499999999 7.733095499999999 7.733095499999999 ZT8-11 6.570159 6.570159 6.570159 ZT12-15 6.9571235 6.9571235 6.9571235 ZT16-19 7.571014 7.571014 7.571014 ZT20-23 6.8815835 6.8815835 6.8815835