condition mean min max ZT0-3 17.801426 17.801426 17.801426 ZT4-7 18.4709705 18.4709705 18.4709705 ZT8-11 16.449591 16.449591 16.449591 ZT12-15 15.819322500000002 15.819322500000002 15.819322500000002 ZT16-19 15.8472485 15.8472485 15.8472485 ZT20-23 15.852615 15.852615 15.852615