condition mean min max ZT0-3 6.645424 6.645424 6.645424 ZT4-7 8.4785725 8.4785725 8.4785725 ZT8-11 7.3934495 7.3934495 7.3934495 ZT12-15 7.258725500000001 7.258725500000001 7.258725500000001 ZT16-19 6.9052525 6.9052525 6.9052525 ZT20-23 7.39967 7.39967 7.39967