How do the attributes work?

Сoncentration and evasion  by what formula is the calculation?

as far as I know, nobody has managed to work out how this is calculated. But I have made a few assumptions (don't know if there right or wrong).
Personally I would guess that if you and the target have = Con Vs Eva then you probably have a 50% hit chance. So for now im going by this assumption that the calculation is something like Con / Eva X 50.
only problem its every hard test without a lot of peeps with varying amounts of Con and Eva.