Research Article

Evaluating the Longitudinal Item and Category Stability of the SF-36 Full and Summary Scales Using Rasch Analysis

Table 11

SF-36 physical health scale Rasch analysis of summary of category structure for six waves of data collection.

WAVE 1WAVE 2WAVE 3
CAT.
LABEL
NAverage MeasuresInfit MnSqOutfit MnSqAndrich ThresholdsNAverage MeasuresInfit MnSqOutfit MnSqAndrich ThresholdsNAverage MeasuresInfit MnSqOutfit MnSqAndrich Thresholds

16072123(-3.86)1.181.11NONE5535025( -3.92)1.121.07NONE4699528( -3.86)1.141.08NONE
28303932-2.13.93.94-2.567045432-2.19.93.92-2.605469232-2.171.00.99-2.54
37329928-.83.66.59-1.546278029-.85.66.60-1.614690528-.90.72.62-1.61
4129575.101.191.26.59113895.141.211.38.5397206.071.111.11.38
51514461.961.051.15-.71263462.031.131.33-.5994262.051.081.17-.5
62380(5.32)2.672.614.212330(5.34)3.182.984.231550(5.43)2.772.304.33

WAVE 4WAVE 5WAVE 6
CAT.
LABEL
N%Average MeasuresInfit MnSqOutfit MnSqAndrich ThresholdsN%Average MeasuresInfit MnSqOutfit MnSqAndrich ThresholdsN%Average MeasuresInfit MnSqOutfit MnSqAndrich Thresholds

14292429( -3.75)1.151.08NONE3650231( -3.66)1.151.08NONE2878736( -3.64)1.151.08NONE
24460330-2.091.051.02-2.423375129-2.011.081.01-2.332323329-2.021.101.01-2.30
33607124-.89.76.64-1.522538922-.87.82.68-1.441693021-.91.86.73-1.46
489586.061.00.96.2473106.06.94.86.1353537.01.91.80.03
5859262.011.101.16-.4646461.961.091.12-.3469462.001.091.10-.3
61500(5.29)2.542.024.181290(5.12)2.251.754.02800(5.24)2.031.524.13

Notes.Andrich threshold category increase of >5; Andrich threshold category decrease where an increase is expected; values in italic for Infit or Outfit MnSq > 1.34; values underlined for Infit or Outfit MnSq < 0.64.