condition mean min max ZT0-3 8.7 8.7 8.7 ZT4-7 5.1 5.1 5.1 ZT8-11 5.75 5.75 5.75 ZT12-15 23.900000000000002 23.900000000000002 23.900000000000002 ZT16-19 18.6 18.6 18.6 ZT20-23 17.25 17.25 17.25