condition mean min max ZT0-3 4.114615 4.114615 4.114615 ZT4-7 6.0534775000000005 6.0534775000000005 6.0534775000000005 ZT8-11 5.95624 5.95624 5.95624 ZT12-15 6.03618 6.03618 6.03618 ZT16-19 5.47273 5.47273 5.47273 ZT20-23 4.943709166666666 4.943709166666666 4.943709166666666