The inherent variability of a rock mass is difficult to model and for this reason engineers very often have to ask the question "What value should be used in analyses?" The answer to such question requires a probabilistic approach in the evaluating the uncertainty in the input parameters in geologic media. In the recent times, specialists have encountered problems in the input parameters derived from uncertainty modelling based on the Fuzzy set theory, Monte Carlo Simulation, Latin Hypercube Sampling etc.