I have a list of categories A, B, C, etc, each with a probability:
 
    A   .015
    B   .005
    C   .02
    D    ... etc. 

I need to find if the difference between two of these categories, say
     
    diff(C,A) = .02 - .015 = 0.005

is statistically significant. Since I don't have a normal distribution (and obviously not even continuous), what test would be recommended?