Are probabilisitc algorithms deterministic?
A probabilistic algorithm is one which has access to the output of a random source during its computation. It might be the case that although the algorithm uses randomness, the output is deterministic, i.e. for every possible random string obtained from the source the output is the same (you can always just ignore the source and act solely on the input).

Note that when you're dealing with probabilistic algorithms, your output becomes a random variable. The output can be deterministic in the sense that it is always the same, or can take some value with probability 1 (which is a weaker statement).