condition mean min max ZT0-3 4.060303333333334 2.36678 5.05384 ZT4-7 4.27622 4.27622 4.27622 ZT8-11 3.5201450000000003 3.5201450000000003 3.5201450000000003 ZT12-15 6.5777375 6.046155 7.10932 ZT16-19 7.322865 7.322865 7.322865 ZT20-23 7.37392 7.37392 7.37392