condition mean min max ZT0-3 7.617747 7.617747 7.617747 ZT4-7 7.422596 7.422596 7.422596 ZT8-11 6.9837395 6.9837395 6.9837395 ZT12-15 6.5489885 6.5489885 6.5489885 ZT16-19 7.3144825 7.3144825 7.3144825 ZT20-23 6.419795 6.419795 6.419795