condition mean min max ZT0-3 2.273851666666667 2.01144 2.6787 ZT4-7 2.4741 2.4741 2.4741 ZT8-11 2.781675 2.781675 2.781675 ZT12-15 5.66936 5.21458 6.124140000000001 ZT16-19 5.019185 5.019185 5.019185 ZT20-23 4.7409 4.7409 4.7409