condition mean min max ZT0-3 8.573861 8.573861 8.573861 ZT4-7 8.877452000000002 8.877452000000002 8.877452000000002 ZT8-11 8.7486905 8.7486905 8.7486905 ZT12-15 8.5316455 8.5316455 8.5316455 ZT16-19 8.732762000000001 8.732762000000001 8.732762000000001 ZT20-23 8.357715 8.357715 8.357715