condition mean min max ZT0-3 20.009243 20.009243 20.009243 ZT4-7 17.630215999999997 17.630215999999997 17.630215999999997 ZT8-11 15.5115355 15.5115355 15.5115355 ZT12-15 17.700038 17.700038 17.700038 ZT16-19 19.454680500000002 19.454680500000002 19.454680500000002 ZT20-23 20.494354 20.494354 20.494354