condition mean min max ZT0-3 7.807372 7.807372 7.807372 ZT4-7 7.553955 7.553955 7.553955 ZT8-11 6.8553625 6.8553625 6.8553625 ZT12-15 7.2512039999999995 7.2512039999999995 7.2512039999999995 ZT16-19 7.4635845 7.4635845 7.4635845 ZT20-23 8.494683 8.494683 8.494683