condition mean min max ZT0-3 14.577886 14.577886 14.577886 ZT4-7 16.258551999999998 16.258551999999998 16.258551999999998 ZT8-11 18.0453585 18.0453585 18.0453585 ZT12-15 15.161845 15.161845 15.161845 ZT16-19 16.966935499999998 16.966935499999998 16.966935499999998 ZT20-23 20.4092615 20.4092615 20.4092615