A method, program and system for computing an accurate compatibility index value based on an individual's measured psychological traits. Empirically derived numeric values relating to answer choices collected during psychological testing are weighted and combined to represent a probability of the individual's traits. The sum of item steps is used to derive a standardized value of the individual's trait level on the factor being measured. Rasch scaling techniques convert the scores to an interval scale to allow for invariant comparison of the various trait levels. A compatibility index value is achieved by performing multiple comparisons between two individuals, taking into account each individual's scores for each factor measured. The compatibility index is a number that is directly related to the strength of the match between the individuals.