condition mean min max ZT0-3 7.701743 7.701743 7.701743 ZT4-7 9.264824 9.264824 9.264824 ZT8-11 8.752823 8.752823 8.752823 ZT12-15 8.0964325 8.0964325 8.0964325 ZT16-19 8.659687000000002 8.659687000000002 8.659687000000002 ZT20-23 7.5756765 7.5756765 7.5756765