condition mean min max ZT0-3 2.4735216666666666 2.02069 2.8072299999999997 ZT4-7 2.270055 2.270055 2.270055 ZT8-11 3.5285450000000003 3.5285450000000003 3.5285450000000003 ZT12-15 4.4887525 3.736955 5.24055 ZT16-19 4.31574 4.31574 4.31574 ZT20-23 2.9303150000000002 2.9303150000000002 2.9303150000000002