condition mean min max ZT0-3 8.4 8.4 8.4 ZT4-7 1.5 1.5 1.5 ZT8-11 16.900000000000002 16.900000000000002 16.900000000000002 ZT12-15 7.800000000000001 7.800000000000001 7.800000000000001 ZT16-19 2.9000000000000004 2.9000000000000004 2.9000000000000004 ZT20-23 7.449999999999999 7.449999999999999 7.449999999999999