condition mean min max ZT0-3 6.642685 6.642685 6.642685 ZT4-7 6.7914650000000005 6.7914650000000005 6.7914650000000005 ZT8-11 7.3102045 7.3102045 7.3102045 ZT12-15 7.016919 7.016919 7.016919 ZT16-19 7.3353915 7.3353915 7.3353915 ZT20-23 7.810931 7.810931 7.810931