condition mean min max ZT0-3 2.1137916666666667 1.85631 2.370905 ZT4-7 2.70655 2.70655 2.70655 ZT8-11 2.2697000000000003 2.2697000000000003 2.2697000000000003 ZT12-15 3.3108449999999996 3.00998 3.6117099999999995 ZT16-19 3.147175 3.147175 3.147175 ZT20-23 3.299915 3.299915 3.299915