condition mean min max ZT0-3 18.200000000000003 18.200000000000003 18.200000000000003 ZT4-7 2.1 2.1 2.1 ZT8-11 19.75 19.75 19.75 ZT12-15 8.600000000000001 8.600000000000001 8.600000000000001 ZT16-19 13.65 13.65 13.65 ZT20-23 4.1 4.1 4.1