condition mean min max ZT0-3 19.045454 19.045454 19.045454 ZT4-7 19.2666295 19.2666295 19.2666295 ZT8-11 21.197136999999998 21.197136999999998 21.197136999999998 ZT12-15 18.570742 18.570742 18.570742 ZT16-19 20.5811445 20.5811445 20.5811445 ZT20-23 17.658426 17.658426 17.658426