condition mean min max ZT0-3 14.855675 13.64995 16.0614 ZT4-7 9.286485 9.286485 9.286485 ZT8-11 7.713975 7.713975 7.713975 ZT12-15 0 0 0 ZT16-19 12.4154 12.4154 12.4154 ZT20-23 11.7915 11.7915 11.7915