The probability of each resident being derived from a baseline reference population is determined by comparing the genotype of each resident to baseline allele frequencies.  Please note that a resident trout collection is not present in the baseline.  An optimal reference genetic baseline contains all potential stock sources for an unknown sample.  Since it is unknown whether the resident trout are a distinct stock, the individual assignment analysis should be interpreted as providing information about which steelhead stock present in the baseline is the most similar to each resident.