condition mean min max ZT0-3 7.623239 7.623239 7.623239 ZT4-7 8.661587 8.661587 8.661587 ZT8-11 9.800741 9.800741 9.800741 ZT12-15 8.4591535 8.4591535 8.4591535 ZT16-19 8.667002 8.667002 8.667002 ZT20-23 7.9277785000000005 7.9277785000000005 7.9277785000000005