condition mean min max ZT0-3 8.965595 8.965595 8.965595 ZT4-7 7.499855 7.499855 7.499855 ZT8-11 9.330545 9.330545 9.330545 ZT12-15 9.483735 9.483735 9.483735 ZT16-19 11.49545 11.49545 11.49545 ZT20-23 9.729795 9.729795 9.729795