condition mean min max ZT0-3 7.966209 7.966209 7.966209 ZT4-7 8.664742 8.664742 8.664742 ZT8-11 7.9377580000000005 7.9377580000000005 7.9377580000000005 ZT12-15 8.3171385 8.3171385 8.3171385 ZT16-19 7.704451000000001 7.704451000000001 7.704451000000001 ZT20-23 8.008999 8.008999 8.008999