condition mean min max ZT0-3 9.122406 9.122406 9.122406 ZT4-7 7.944915 7.944915 7.944915 ZT8-11 8.3686655 8.3686655 8.3686655 ZT12-15 8.329930000000001 8.329930000000001 8.329930000000001 ZT16-19 9.449641499999998 9.449641499999998 9.449641499999998 ZT20-23 8.971326999999999 8.971326999999999 8.971326999999999