condition mean min max ZT0-3 17.507505 17.507505 17.507505 ZT4-7 20.759962 20.759962 20.759962 ZT8-11 17.7681815 17.7681815 17.7681815 ZT12-15 18.876668000000002 18.876668000000002 18.876668000000002 ZT16-19 17.0470835 17.0470835 17.0470835 ZT20-23 19.1577735 19.1577735 19.1577735