condition mean min max ZT0-3 19.849999999999998 19.849999999999998 19.849999999999998 ZT4-7 6.6 6.6 6.6 ZT8-11 12.8 12.8 12.8 ZT12-15 17.95 17.95 17.95 ZT16-19 20.0 20.0 20.0 ZT20-23 16.15 16.15 16.15