condition mean min max ZT0-3 8.295155 7.902105000000001 8.838085 ZT4-7 6.935755 6.935755 6.935755 ZT8-11 7.86797 7.86797 7.86797 ZT12-15 9.8561425 8.705695 11.00659 ZT16-19 10.516549999999999 10.516549999999999 10.516549999999999 ZT20-23 13.59225 13.59225 13.59225