Tracking techniques may be used to reduce the ambiguity of an acoustic source’s position in matched-field processing, particularly for low signal-to-noise ratios. An efficient tracking algorithm was recently described, in which the performance would be comparable to that of an exhaustive tracker; that is, the probability that the source track is examined is close to unity for cases of interest. The current paper describes an efficient technique to estimate the probability that the source track is examined. The procedure involves the use of noise-only data to define statistical thresholds for the strongest peaks in the ambiguity surface. Once these thresholds are defined, the required probabilities may be estimated by evaluating the ambiguity function for signal-plus-noise data within a small region surrounding the known source location, and identifying any peaks exceeding the thresholds. Results of simulations obtained for a slanted array indicate that this approach provides an effective way to estimate the probability that the source track is examined.