Development and validation of a 12-item version of the Barrett-Lennard Relationship Inventory (B-L RI:mini) using item response theory

The Barrett-Lennard Relationship Inventory (B-L RI; Barrett-Lennard, (2015). The Relationship Inventory A Complete Resource and Guide. http://nbn-resolving.de/urn:nbn:de:101:1-201602103917) is the most widely used measure of the facilitative conditions described by Carl Rogers as important for constructive personality development in his person-centered theory. At with 64 items it is however time consuming for participants to complete, and even in its shorter form, the B-L RI is 40-items long. In order to improve its utility, a mini form of the B-L RI was developed. In study 1, we used item response theory to select 12 out of the full 64 items to form the B-L RI:mini based on their discrimination, difficulty, information, and measurement invariance across the English (n = 298), Chinese (n = 658), and Spanish (n = 330) language versions of the inventory. In study 2 (N= 362), we validated the reliability and validity of the new 12-item measure. It was found that the B-L RI:mini showed excellent total internal consistency, temporal stability, and construct validity. According to the results of the study, the B-L RI:mini maintains optimal psychometric properties with a small number of items. This scale is recommended for use in further studies.