condition mean min max ZT0-3 4.689275 4.095345 5.155335 ZT4-7 6.8698999999999995 6.8698999999999995 6.8698999999999995 ZT8-11 6.934455 6.934455 6.934455 ZT12-15 9.386845000000001 8.49674 10.27695 ZT16-19 9.295929999999998 9.295929999999998 9.295929999999998 ZT20-23 8.857765 8.857765 8.857765