condition mean min max ZT0-3 4.659081666666667 2.788185 5.93635 ZT4-7 6.14376 6.14376 6.14376 ZT8-11 2.50593 2.50593 2.50593 ZT12-15 3.538095 3.4843200000000003 3.59187 ZT16-19 3.8278550000000005 3.8278550000000005 3.8278550000000005 ZT20-23 2.8346400000000003 2.8346400000000003 2.8346400000000003