condition mean min max ZT0-3 7.527422 7.527422 7.527422 ZT4-7 8.172368 8.172368 8.172368 ZT8-11 7.716999 7.716999 7.716999 ZT12-15 7.860447499999999 7.860447499999999 7.860447499999999 ZT16-19 8.0279475 8.0279475 8.0279475 ZT20-23 8.950922 8.950922 8.950922