condition mean min max ZT0-3 18.87515 18.87515 18.87515 ZT4-7 15.9633 15.9633 15.9633 ZT8-11 13.7467 13.7467 13.7467 ZT12-15 15.5592 15.5592 15.5592 ZT16-19 20.38935 20.38935 20.38935 ZT20-23 19.59855 19.59855 19.59855