Background: The Personal Outcomes Scale (POS) is a scale developed to measure quality of life of adults (18+) with intellectual disability. Previous studies have reported good fit for Spanish and Portuguese language versions of POS.
Aims: This study aimed to evaluate the factor structure of the English language version of POS when used to measure the quality of life of adults (18+) with intellectual disability in the UK.
Materials and methods: Analysis was conducted on POS data from 310 adults with an intellectual disability. First and second order factor models and multi-level models were used to assess fit.
Results: There was poor fit to the data for all tested models. We estimated that 23% of variance in POS scores was accounted for by interviewer cluster.
Discussion: This was the first UK-based evaluation of POS and our data did not confirm the factor structure of the POS measure. The identification of systematic variability within the dataset indicates that inter-rater reliability is a potential limitation of the POS tool.
Conclusion: Further research is needed to investigate inter-rater reliability of POS interviewers and to explore factor structure.
Keywords: factor analysis; intellectual disability; psychometric testing; quality of life.
© 2023 The Authors. Journal of Applied Research in Intellectual Disabilities published by John Wiley & Sons Ltd.