condition mean min max ZT0-3 3.336205 2.704835 4.233755 ZT4-7 2.281485 2.281485 2.281485 ZT8-11 1.90462 1.90462 1.90462 ZT12-15 2.91188 2.35269 3.47107 ZT16-19 3.35364 3.35364 3.35364 ZT20-23 5.28833 5.28833 5.28833