condition mean min max ZT0-3 8.430413 8.430413 8.430413 ZT4-7 7.548902999999999 7.548902999999999 7.548902999999999 ZT8-11 7.9288605 7.9288605 7.9288605 ZT12-15 7.5935505 7.5935505 7.5935505 ZT16-19 8.255312499999999 8.255312499999999 8.255312499999999 ZT20-23 7.5916885 7.5916885 7.5916885