
For effect and points items, the chances are as follows;
Coeff 1; 1/2
Coeff 2; 1/3
Coeff 3; 1/8
Coeff 4; 3/200
Coeff 5; 1/700
Coeff 6; 1/22000
So, if you want to figure out the chance of a certain item appearing (

([Coeff chance {3}] * [1/{# of type of item (effect)}]) * (# of levels you do, on average, per playthrough [Probably about 40])
So,
([1/8] * [1/25]) * 40 = 1/5.
Thus, you have about a 1/5 chance of getting a
