The base stats are the same for any Pokemon of the species. The thing that differs with level is the CP Multiplier.
I don't know the details about this, this is all I know.
The base stats are multiplied to each other, with attack stat having a higher weighting while defence and stamina being equal.
Do take note that the base stats are MULTIPLIED to each other, not added. So, there can be cases where a Pokemon has higher attack stat and higher base stat total, yet lower CP (e.g. Cloyster vs Lapras).