This is part 2 of a series, see part 1 first.
When you fire a shot, you can hit or miss. A hit can penetrate or not. A penetrating hit can damage or not. Damage can vary according to the random generator. Lot of variables, but all can only depend on tank stats, player skill and random generator.
I gathered data from 374 matches. All from the same tank, same gun: AT15, B-barrel. During these matches I faced practically every tank randomly, the large number (15*374 = 5610 enemies) guarantee that I had an "average target tank". My skill couldn't change much as I've had more than a thousand matches with British TDs and more than a hundred with AT15 itself. The only factor remaining is random luck. Let's see how random it is.