condition mean min max ZT0-3 7.904578333333334 6.387225000000001 8.8322 ZT4-7 4.05009 4.05009 4.05009 ZT8-11 3.2967500000000003 3.2967500000000003 3.2967500000000003 ZT12-15 4.6179575 4.326145 4.90977 ZT16-19 4.283905000000001 4.283905000000001 4.283905000000001 ZT20-23 10.1554 10.1554 10.1554