condition mean min max ZT0-3 20.672301 20.672301 20.672301 ZT4-7 15.104198 15.104198 15.104198 ZT8-11 17.5588355 17.5588355 17.5588355 ZT12-15 14.997636499999999 14.997636499999999 14.997636499999999 ZT16-19 17.511664500000002 17.511664500000002 17.511664500000002 ZT20-23 15.392339 15.392339 15.392339