The Combination Analysis option in Swedge is not, strictly speaking, a Probabilistic Analysis. Therefore it is important to note the following differences:
A Probability of Failure is NOT reported after a Combination Analysis. However, if desired, a Probability of Failure can be calculated by dividing the total number of failed wedges by the total number of joint combinations. The applicability of a Probability of Failure calculated from a Combination analysis depends on the nature of the input data (e.g. was the analysis computed for a single global orientation file or two discrete joint sets?). The interpretation of results in this regard is the responsibility of the user.
The Probability of Failure is by definition an outcome of some type of statistical analysis. If the Combination Analysis only considers a small sample of a few discrete joint measurements, then clearly this may not be representative of results obtained from a larger sample size, or a probabilistic analysis based on reliable statistical distributions of joint orientations. If the Combination Analysis considers a large enough data set, then the Probability of Failure may be comparable to results obtained from a probabilistic analysis. Furthermore, results from the intersection of two particular joint sets are not going to be the same as results which consider all possible orientations.