condition mean min max ZT0-3 8.767846 8.767846 8.767846 ZT4-7 8.292637 8.292637 8.292637 ZT8-11 8.789223 8.789223 8.789223 ZT12-15 8.537255 8.537255 8.537255 ZT16-19 7.765103 7.765103 7.765103 ZT20-23 8.2469355 8.2469355 8.2469355