condition mean min max ZT0-3 7.833307 7.833307 7.833307 ZT4-7 7.7044005 7.7044005 7.7044005 ZT8-11 8.028235 8.028235 8.028235 ZT12-15 8.4796835 8.4796835 8.4796835 ZT16-19 7.749213 7.749213 7.749213 ZT20-23 8.5233935 8.5233935 8.5233935