condition mean min max ZT0-3 6.237855 6.237855 6.237855 ZT4-7 2.03309 2.03309 2.03309 ZT8-11 2.2373399999999997 2.2373399999999997 2.2373399999999997 ZT12-15 4.586935 4.586935 4.586935 ZT16-19 5.0396149999999995 5.0396149999999995 5.0396149999999995 ZT20-23 3.96342 3.96342 3.96342