condition mean min max ZT0-3 7.922545 7.922545 7.922545 ZT4-7 6.8003599999999995 6.8003599999999995 6.8003599999999995 ZT8-11 6.379075 6.379075 6.379075 ZT12-15 8.01369 8.01369 8.01369 ZT16-19 7.8076 7.8076 7.8076 ZT20-23 6.755245 6.755245 6.755245