Evaluating the Longitudinal Item and Category Stability of the SF-36 Full and Summary Scales Using Rasch Analysis
Table 17
SF-36 mental health scale Rasch analysis of summary of category structure for six waves of data collection.
WAVE 1
WAVE 2 (p. 120)
WAVE 3 (p. 125)
CAT. LABEL
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Threshold
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Threshold
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Threshold
1
22667
14
( -3.07)
1.38
1.20
NONE
18463
13
( -3.18)
1.41
1.22
NONE
14323
12
( -3.18)
1.38
1.22
NONE
2
49420
30
-1.06
.75
.78
-1.91
43019
30
-1.08
.76
.81
-2.03
33416
28
-1.12
.78
.85
-2.02
3
15086
9
-.17
.96
.86
.66
12291
8
-.15
.97
.89
.71
10845
9
-.17
.98
.85
.57
4
25646
15
.40
1.02
1.11
-.4
20753
14
.43
1.00
1.12
-.3
18002
15
.44
1.00
1.06
-.3
5
28636
17
1.14
1.06
1.31
.5
24231
17
1.16
1.08
1.38
.5
18787
16
1.20
1.13
1.28
.63
6
24973
15
(2.54)
1.00
1.07
1.15
23360
16
(2.56)
1.00
1.08
1.17
18313
15
(2.60)
.95
1.02
1.19
WAVE 4
WAVE 5
WAVE 6
CAT. LABEL
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Threshold
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Threshold
N
%
Average Measures
Infit MnSq
Outfit MnSq
Andrich Threshold
1
12561
13
( -3.08)
1.37
1.21
NONE
10333
14
( -3.00)
1.38
1.23
NONE
7471
14
( -2.98)
1.37
1.21
NONE
2
27233
29
-1.11
.80
.88
-1.91
20854
28
-1.08
.82
.89
-1.82
14529
27
-1.09
.83
.91
-1.80
3
9548
10
-.18
.98
.82
.51
7515
10
-.19
.94
.76
.50
5675
11
-.19
.94
.78
.43
4
15240
16
.42
1.00
1.00
-.3
12348
17
.40
.97
.94
-.4
9024
17
.41
.98
.94
-.3
5
15741
16
1.17
1.14
1.22
.60
12183
16
1.15
1.19
1.27
.61
8698
16
1.15
1.19
1.24
.64
6
15147
16
(2.57)
.93
.99
1.16
11454
15
(2.53)
.90
.99
1.11
8415
16
(2.51)
.90
.96
1.07
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.
