condition mean min max ZT0-3 8.381048 8.381048 8.381048 ZT4-7 7.797508499999999 7.797508499999999 7.797508499999999 ZT8-11 7.820162 7.820162 7.820162 ZT12-15 8.7049035 8.7049035 8.7049035 ZT16-19 7.9986365 7.9986365 7.9986365 ZT20-23 7.9348955 7.9348955 7.9348955