condition mean min max ZT0-3 8.682661 8.682661 8.682661 ZT4-7 8.1763665 8.1763665 8.1763665 ZT8-11 8.6351635 8.6351635 8.6351635 ZT12-15 9.0990255 9.0990255 9.0990255 ZT16-19 8.067602 8.067602 8.067602 ZT20-23 8.94474 8.94474 8.94474