condition mean min max ZT0-3 8.901485 8.901485 8.901485 ZT4-7 9.836981999999999 9.836981999999999 9.836981999999999 ZT8-11 8.6933845 8.6933845 8.6933845 ZT12-15 7.813254000000001 7.813254000000001 7.813254000000001 ZT16-19 9.704719 9.704719 9.704719 ZT20-23 8.544203 8.544203 8.544203