condition mean min max ZT0-3 2.114682 0.808386 3.046895 ZT4-7 1.1913315 1.1913315 1.1913315 ZT8-11 0.378094 0.378094 0.378094 ZT12-15 1.26579525 0.7765205 1.75507 ZT16-19 1.7752400000000002 1.7752400000000002 1.7752400000000002 ZT20-23 2.440945 2.440945 2.440945