condition mean min max ZT0-3 5.056788333333333 3.756995 6.027645 ZT4-7 3.445665 3.445665 3.445665 ZT8-11 4.19803 4.19803 4.19803 ZT12-15 6.6825399999999995 5.741709999999999 7.6233699999999995 ZT16-19 7.3054749999999995 7.3054749999999995 7.3054749999999995 ZT20-23 7.679175 7.679175 7.679175