Evaluation of the MOS SF-36 Physical Functioning Scale (PF-10): II. Comparison of relative precision using Likert and Rasch scoring methods
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UMass Chan Affiliations
Department of Quantitative Health SciencesDocument Type
Journal ArticlePublication Date
1997-04-01Keywords
*Data Interpretation, Statistical*Health Status Indicators
Heart Failure
Humans
Linear Models
Psychometrics
Severity of Illness Index
Biostatistics
Epidemiology
Health Services Research
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This study examined the relative precision (RP) of two methods of scoring the 10-item Physical Functioning Scale (PF-10) from a large sample of patients (n = 3445) of the Medical Outcomes Study. Based on a Likert scaling model, the PF-10 summated scoring method was compared with a Rasch Item Response Theory (IRT) scaling model in which raw scores were transformed into a latent trait variable of physical functioning. Potential differences between scoring methods were hypothesized to be attributed to: (1) the logarithmic nature of the Rasch transformation; (2) the unevenness of the PF-10 item distributions; and (3) reduction of within-group variance. RP ratios favored the Rasch model in discriminating between patients who differed in disease severity. The Rasch and Likert scoring models performed similarly for tests involving sensitivity to change over a two-year follow-up period. In all comparisons, differences between methods were most apparent in clinical groups whose scores most approximated the extremes of the score distribution. Further research is necessary to test for differences between scoring models in discrimination and sensitivity to change among clinical groups whose scores are sufficiently spread across the continuum of physical functioning, in particular patients with either very high or low physical functioning. The Rasch model of scoring may have important implications for the clinical interpretation of individual scores at all ranges of the scale.Source
J Clin Epidemiol. 1997 Apr;50(4):451-61. Link to article on publisher's siteDOI
10.1016/S0895-4356(96)00424-6Permanent Link to this Item
http://hdl.handle.net/20.500.14038/47399PubMed ID
9179104Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1016/S0895-4356(96)00424-6