condition mean min max ZT0-3 7.325853 7.325853 7.325853 ZT4-7 8.0622595 8.0622595 8.0622595 ZT8-11 8.13981 8.13981 8.13981 ZT12-15 8.1546485 8.1546485 8.1546485 ZT16-19 8.4392265 8.4392265 8.4392265 ZT20-23 8.074897 8.074897 8.074897