condition mean min max ZT0-3 6.6932 6.6932 6.6932 ZT4-7 6.7855799999999995 6.7855799999999995 6.7855799999999995 ZT8-11 6.63729 6.63729 6.63729 ZT12-15 6.768583333333334 6.768583333333334 6.768583333333334 ZT16-19 6.75364 6.75364 6.75364 ZT20-23 6.57355 6.57355 6.57355