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 1
WAVE 2
WAVE 3
CAT. LABEL
N
Average Measures
Infit MnSq
Outfit MnSq
Andrich Thresholds
N
Average Measures
Infit MnSq
Outfit MnSq
Andrich Thresholds
N
Average Measures
Infit MnSq
Outfit MnSq
Andrich Thresholds
1
60721
23
(-3.86)
1.18
1.11
NONE
55350
25
( -3.92)
1.12
1.07
NONE
46995
28
( -3.86)
1.14
1.08
NONE
2
83039
32
-2.13
.93
.94
-2.56
70454
32
-2.19
.93
.92
-2.60
54692
32
-2.17
1.00
.99
-2.54
3
73299
28
-.83
.66
.59
-1.54
62780
29
-.85
.66
.60
-1.61
46905
28
-.90
.72
.62
-1.61
4
12957
5
.10
1.19
1.26
.59
11389
5
.14
1.21
1.38
.53
9720
6
.07
1.11
1.11
.38
5
15144
6
1.96
1.05
1.15
-.7
12634
6
2.03
1.13
1.33
-.5
9942
6
2.05
1.08
1.17
-.5
6
238
0
(5.32)
2.67
2.61
4.21
233
0
(5.34)
3.18
2.98
4.23
155
0
(5.43)
2.77
2.30
4.33
WAVE 4
WAVE 5
WAVE 6
CAT. LABEL
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Thresholds
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Thresholds
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Thresholds
1
42924
29
( -3.75)
1.15
1.08
NONE
36502
31
( -3.66)
1.15
1.08
NONE
28787
36
( -3.64)
1.15
1.08
NONE
2
44603
30
-2.09
1.05
1.02
-2.42
33751
29
-2.01
1.08
1.01
-2.33
23233
29
-2.02
1.10
1.01
-2.30
3
36071
24
-.89
.76
.64
-1.52
25389
22
-.87
.82
.68
-1.44
16930
21
-.91
.86
.73
-1.46
4
8958
6
.06
1.00
.96
.24
7310
6
.06
.94
.86
.13
5353
7
.01
.91
.80
.03
5
8592
6
2.01
1.10
1.16
-.4
6464
6
1.96
1.09
1.12
-.3
4694
6
2.00
1.09
1.10
-.3
6
150
0
(5.29)
2.54
2.02
4.18
129
0
(5.12)
2.25
1.75
4.02
80
0
(5.24)
2.03
1.52
4.13
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.