Table 5.

McFadden's Pseudo R2 and IRT Parameters for Items Displaying DIF (Likelihood-Ratio χ² Test Criterion of 0.01)

Item With DIF Number and Content	DIF Type	McFadden's Pseudo R2	Slope; and Threshold Parameters
Items with DIF for gender: CAT9: Looking after appearance	Uniforma	R212b = 0.031 R223c = 0.002*	Male Female	2.39; 1.03, 2.04 1.98; 0.47, 1.77
Items with DIF for age: CAT42: Feeling embarrassed	Uniform	R212 = 0.025 R223 = 0.002*	<=75 >75	2.33; 1.43d 1.88; 2.11
Items with DIF for independently completed vs. with help: CAT 35: Feeling worried or concerned about your safety at home	Nonuniforme	R212 = 0.011* R223 = 0.023	Independent With help	2.37; 1.27d 0.99; 2.23

^aDIF that is proportional across levels of the underlying latent trait.

^bR²₁₂ represents nonuniform DIF.

^cR²₂₃ represents uniform DIF.

^dCAT42 and CAT35, both located at one end (high disability) of the disability continuum, and response category ‘often/always’ (collapsed) was hardly chosen, therefore one threshold parameter was calculated, representing threshold between categories ‘never’ and ‘sometimes’.

^eDIF that is nonproportional across levels of the underlying latent trait.

^*DIF type that exceeds the test criterion of 0.01.