condition mean min max ZT0-3 8.705555 8.705555 8.705555 ZT4-7 8.3095635 8.3095635 8.3095635 ZT8-11 8.204958 8.204958 8.204958 ZT12-15 8.4211065 8.4211065 8.4211065 ZT16-19 8.0377685 8.0377685 8.0377685 ZT20-23 8.645554 8.645554 8.645554