condition mean min max ZT0-3 2.007349666666667 0.762419 2.732355 ZT4-7 1.442026 1.442026 1.442026 ZT8-11 1.95397 1.95397 1.95397 ZT12-15 4.1643675 3.29333 5.035405 ZT16-19 4.3782250000000005 4.3782250000000005 4.3782250000000005 ZT20-23 3.711295 3.711295 3.711295