condition mean min max ZT0-3 8.034219 8.034219 8.034219 ZT4-7 7.7825435 7.7825435 7.7825435 ZT8-11 8.406006 8.406006 8.406006 ZT12-15 8.2780205 8.2780205 8.2780205 ZT16-19 7.857549000000001 7.857549000000001 7.857549000000001 ZT20-23 7.9649915 7.9649915 7.9649915