condition mean min max ZT0-3 8.158927 8.158927 8.158927 ZT4-7 8.5495525 8.5495525 8.5495525 ZT8-11 8.088258 8.088258 8.088258 ZT12-15 7.6760895 7.6760895 7.6760895 ZT16-19 8.175347 8.175347 8.175347 ZT20-23 8.2667585 8.2667585 8.2667585