condition mean min max ZT0-3 7.208888889 7.208888889 7.208888889 ZT4-7 6.3438888890000005 6.3438888890000005 6.3438888890000005 ZT8-11 6.053888888666666 6.053888888666666 6.053888888666666 ZT12-15 5.774444444333334 5.774444444333334 5.774444444333334 ZT16-19 5.201111111 5.201111111 5.201111111 ZT20-23 5.21 5.21 5.21