condition mean min max ZT0-3 15.646958333333334 9.334925 21.18485 ZT4-7 8.166474999999998 8.166474999999998 8.166474999999998 ZT8-11 7.384295 7.384295 7.384295 ZT12-15 11.5104275 10.607005000000001 12.41385 ZT16-19 15.6588 15.6588 15.6588 ZT20-23 19.051000000000002 19.051000000000002 19.051000000000002