condition mean min max ZT0-3 6.924555 6.924555 6.924555 ZT4-7 4.35487 4.35487 4.35487 ZT8-11 6.27785 6.27785 6.27785 ZT12-15 8.552495 8.552495 8.552495 ZT16-19 7.254754999999999 7.254754999999999 7.254754999999999 ZT20-23 7.760865 7.760865 7.760865