condition mean min max ZT0-3 6.065193333333333 6.065193333333333 6.065193333333333 ZT4-7 4.618945 4.618945 4.618945 ZT8-11 5.341635 5.341635 5.341635 ZT12-15 6.4047149999999995 6.4047149999999995 6.4047149999999995 ZT16-19 7.885660000000001 7.885660000000001 7.885660000000001 ZT20-23 7.15328 7.15328 7.15328