condition mean min max ZT0-3 2.294905 2.294905 2.294905 ZT4-7 2.01451 2.01451 2.01451 ZT8-11 1.132085 1.132085 1.132085 ZT12-15 0.6928855 0.6928855 0.6928855 ZT16-19 1.3330700000000002 1.3330700000000002 1.3330700000000002 ZT20-23 1.817555 1.817555 1.817555