condition mean min max ZT0-3 6.992866666666667 6.024615000000001 7.94374 ZT4-7 6.25171 6.25171 6.25171 ZT8-11 6.219245 6.219245 6.219245 ZT12-15 9.064155 8.615515 9.512795 ZT16-19 7.817359999999999 7.817359999999999 7.817359999999999 ZT20-23 8.616335 8.616335 8.616335