condition mean min max ZT0-3 2.1972666666666667 1.921205 2.701695 ZT4-7 6.562885 6.562885 6.562885 ZT8-11 7.696175 7.696175 7.696175 ZT12-15 6.258005 6.031995 6.484014999999999 ZT16-19 5.178324999999999 5.178324999999999 5.178324999999999 ZT20-23 3.8021000000000003 3.8021000000000003 3.8021000000000003