WG-SS items | Fit with the one-dimensional Rasch model | Differential Item Functioning | |||
Overall fit p-value = 0.88, Person separation index = 0.60 | location | Chi square | P-value | Uniform DIF | Non-Uniform DIF |
Seeing | 0.30 | 1.16 | 0.88 | – | – |
Hearing | -0.21 | 0.69 | 0.95 | – | – |
Washing and dressing | 1.04 | 5.53 | 0.24 | age | – |
Walking or climbing steps | -0.88 | 4.57 | 0.33 | age | – |
Remembering or concentrating | -1.27 | 0.53 | 0.97 | – | – |
Communicating | 1.01 | 3.53 | 0.47 | gender, age, occupation | – |
ADL items | Fit with the one-dimensional Rasch model | Differential Item Functioning | |||
Overall fit p-value < 0.0000001, Person separation index = 0.83 | location | Chi square | P-value | Uniform DIF | Non-Uniform DIF |
Feeding | 3.56 | 2.61 | 0.46 | – | – |
Toileting | 0.05 | 7.20 | 0.07 | – | – |
Dressing | -0.98 | 18.34 | 0.0004 | – | – |
Bathing | 2.09 | 2.86 | 0.41 | – | – |
Transferring from bed or chair | -1.26 | 23.55 | 0.00003 | – | – |
Walking | -3.45 | 28.70 | 0.000003 | – | – |
IADL items | Fit with the one-dimensional Rasch model | Differential Item Functioning | |||
Overall fit p-value = 0.0003, Person separation index = 0.87 | location | Chi square | P-value | Uniform DIF | Non-Uniform DIF |
Shopping | -1.17 | 10.53 | 0.03 | – | – |
Preparing meals | 0.96 | 14.82 | 0.01 | gender | – |
Doing light housework | -0.67 | 9.91 | 0.04 | gender | – |
Doing heavy housework | -1.32 | 2.03 | 0.73 | – | – |
Handling finances | -0.51 | 9.60 | 0.05 | education | – |
Using telephone | 2.71 | 8.76 | 0.07 | – | – |