condition mean min max ZT0-3 2.055615 1.94282 2.16841 ZT4-7 1.59605 1.59605 1.59605 ZT8-11 1.301005 1.301005 1.301005 ZT12-15 0 0 0 ZT16-19 2.07883 2.07883 2.07883 ZT20-23 1.875 1.875 1.875