User blog comment:MachineGunSuper/Breaking the odds really hardly?/@comment-35470197-20181005121408

It depends on the definition of the randomness.

If you consider the probability theoretic approach, then you will soon notice that there is no way to define a probability compatible with the addition. (This is what PsiCubed2 said.)

But if you consider a probability incompatible with the addition, the randomness easily makes sense. For example, the normal distribution is often used. (The probability of "\(x\) between \(s\) and \(t\)" is defined as \(\int_s^t \frac{1}{\sqrt[]{\pi}}e^{-x^2} dx\) in this case.)