condition mean min max ZT0-3 8.209305 7.88478 8.53383 ZT4-7 11.409949999999998 11.409949999999998 11.409949999999998 ZT8-11 13.7583 13.7583 13.7583 ZT12-15 0 0 0 ZT16-19 18.3054 18.3054 18.3054 ZT20-23 16.5564 16.5564 16.5564