condition mean min max ZT0-3 17.1 17.1 17.1 ZT4-7 18.6 18.6 18.6 ZT8-11 10.75 10.75 10.75 ZT12-15 11.7 11.7 11.7 ZT16-19 12.899999999999999 12.899999999999999 12.899999999999999 ZT20-23 20.3 20.3 20.3