condition mean min max ZT0-3 7.26642 7.26642 7.26642 ZT4-7 7.255357 7.255357 7.255357 ZT8-11 7.47123 7.47123 7.47123 ZT12-15 8.659417 8.659417 8.659417 ZT16-19 8.357714999999999 8.357714999999999 8.357714999999999 ZT20-23 8.710954000000001 8.710954000000001 8.710954000000001