condition mean min max ZT0-3 33.259227 33.259227 33.259227 ZT4-7 23.2004575 23.2004575 23.2004575 ZT8-11 20.045533 20.045533 20.045533 ZT12-15 17.181525999999998 17.181525999999998 17.181525999999998 ZT16-19 17.2162885 17.2162885 17.2162885 ZT20-23 15.92915 15.92915 15.92915