condition mean min max ZT0-3 3.957675 3.957675 3.957675 ZT4-7 2.810525 2.810525 2.810525 ZT8-11 3.6973599999999998 3.6973599999999998 3.6973599999999998 ZT12-15 4.12224 4.12224 4.12224 ZT16-19 7.446065 7.446065 7.446065 ZT20-23 4.248735 4.248735 4.248735