condition mean min max ZT0-3 6.630475 6.31351 6.918475 ZT4-7 6.93832 6.93832 6.93832 ZT8-11 7.55647 7.55647 7.55647 ZT12-15 8.31154 7.876335000000001 8.746745 ZT16-19 6.315325 6.315325 6.315325 ZT20-23 8.371670000000002 8.371670000000002 8.371670000000002