condition mean min max ZT0-3 18.21965077 17.61946223 18.81983931 ZT4-7 19.44900005 15.17263627 23.72536383 ZT8-11 26.1451775875 23.841096345 28.449258829999998 ZT12-15 16.44666027425 11.684601113500001 21.208719435 ZT16-19 13.537666779999999 12.452228424999998 14.623105135 ZT20-23 20.8688632425 20.09273822 21.644988265000002