condition mean min max ZT0-3 8.605562 8.605562 8.605562 ZT4-7 8.0415205 8.0415205 8.0415205 ZT8-11 7.6578415 7.6578415 7.6578415 ZT12-15 8.1336005 8.1336005 8.1336005 ZT16-19 9.5907755 9.5907755 9.5907755 ZT20-23 8.446746 8.446746 8.446746