Integrating methods to optimize circumplex description and comparison of groups

Using the interpersonal circumplex as an exemplar, this article serves as a methodological primer for integrating techniques of group description and comparison when employing circumplex-based assessment instruments. Circular statistics (Mardia & Jupp, 1999) and the structural summary method (Gurtman & Balakrishnan, 1998) each offer unique and incrementally useful information when applied to group-level data on circumplex measures. Circular statistics offer a set of parameters that are conceptually similar to their linear equivalents (i.e., mean, variance, and confidence intervals). In interpersonal circumplex models, these parameters each provide specific information regarding substantive theme and group homogeneity and allow for the statistical comparison of groups based on the geometry of the circular model. In a similar fashion, the structural summary method for circumplex data provides a set of parameters that complement circular statistics by offering measures of the interpersonal prototypicality of the group profile, levels of profile differentiation and elevation, and a weighted measure of substantive theme. Used in conjunction, these methods offer more information than is available using either in isolation. We provide 4 examples to demonstrate the complementary information the 2 methods provide for assessments employing interpersonal circumplex measures. These examples will allow investigators to generalize the methods to other personality assessment domains in which circumplex models are utilized, such as emotion and vocational preference. [Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Personality Assessment for the following free supplemental resources: an Excel file that calculates the circular statistics and structural summary information described in this article using manually entered octant scores from up to 500 participants.]