Random phenomenon is a situation in which we dont know what the out come is going to come.
Rolling of unbiased dice is a random phenomenon since we dont know what number is going to come. We can only say every number has 1/6 probability.
Rolling a biased coin on other hand also we dont know which number is going to come. We only know every number does not have 1/6 probability.
So does that mean rolling of biased dice is a random phenomenon ?