condition mean min max ZT0-3 6.798156 6.798156 6.798156 ZT4-7 7.9937585 7.9937585 7.9937585 ZT8-11 7.812564999999999 7.812564999999999 7.812564999999999 ZT12-15 7.9993535 7.9993535 7.9993535 ZT16-19 7.739938 7.739938 7.739938 ZT20-23 7.600659 7.600659 7.600659