condition mean min max ZT0-3 7.635728 7.635728 7.635728 ZT4-7 8.5874675 8.5874675 8.5874675 ZT8-11 8.474152 8.474152 8.474152 ZT12-15 8.331788 8.331788 8.331788 ZT16-19 8.250177 8.250177 8.250177 ZT20-23 8.1209505 8.1209505 8.1209505