condition mean min max ZT0-3 7.073575 6.25286 7.89429 ZT4-7 6.5947 6.5947 6.5947 ZT8-11 7.0142 7.0142 7.0142 ZT12-15 0 0 0 ZT16-19 8.538495000000001 8.538495000000001 8.538495000000001 ZT20-23 9.761175 9.761175 9.761175