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. Author manuscript; available in PMC: 2016 Oct 1.
Published in final edited form as: Res Aging. 2014 Sep 15;37(7):671–694. doi: 10.1177/0164027514550834

Figure 2. Measurement Model for the Physical Functioning Measure: Results from SAGES (N=300).

Figure 2

Legend. Structural equation model summarizing the IRT graded response model with 17 ordinal dependent variables. Factor loadings, quantify the correlation between underlying physical functioning and each item. Item thresholds, on a N(0,1) scale, depict the point along the spectrum of physical functioning in which the item has the best discrimination. To scale the physical functioning measure to the metric set for the NIH PROMIS initiative, item factor loadings and threshold parameters for two MOS SF-12 items (limitations in moderate activities and in climbing flights of stairs) were fixed to the values in the PROMIS normative sample. Numbers in parentheses denote standard errors of factor loadings and thresholds. In the figure, item slopes and threshold parameters are reported on a standardized metric, so that parameters are interpretable in correlation and z-score units, respectively.

ADL: Activities of daily living. IADL: Independent activities of daily living. MOS SF-12: Medical Outcomes Study Standard Form 12-item questionnaire.