condition mean min max ZT0-3 6.848195 6.6836649999999995 7.012725 ZT4-7 6.84293 6.84293 6.84293 ZT8-11 5.0061 5.0061 5.0061 ZT12-15 0 0 0 ZT16-19 8.3839 8.3839 8.3839 ZT20-23 7.75735 7.75735 7.75735