Table 1

Lower bounds for the number of items with the maximum score for several studies. N is the number of items that constitute the (sub)scale, Sm is the maximum possible individual item score, n is the reported number of subjects, is the reported mean (sub)scale score, and L is the derived lower bound for the number of items with the maximum score. The last column lists a lower bound for the percentage of items with the maximum score based on L. The second highest possible item score Sm - 1 is equal to Sm - 1 for all considered (sub)scales.
Scale
 N
 Sm
 n
L
Checklist Individual Strength
 Oxford-CFS, CDC94-UCF; Vercoulen et al. [10]
     -fatigue severity subscale
 8
 7
 758
 51.7
 2805
 46%
     -physical activity subscale
 3
 7
 758
 16.9
 0
 0%
     -reduced motivation subscale
 4
 7
 758
 17.0
 0
 0%
     -concentration subscale
 5
 7
 758
 27.5
 0
 0%
Checklist Individual Strength
 CDC94-UCF; van der Werf et al. [21]
     -homebound group; fatigue severity subscale
 8
 7
 18
 53.6
 101
 70%
     -matched ambulant group; fatigue severity subscale
 8
 7
 32
 52.8
 154
 60%
     -total ambulant group; fatigue severity subscale
 8
 7
 270
 52.1
 1107
 51%
     -homebound group; physical activity subscale
 3
 7
 18
 15.8
 0
 0%
     -matched ambulant group; physical activity subscale
 3
 7
 32
 17.0
 0
 0%
     -total ambulant group; physical activity subscale
 3
 7
 270
 17.6
 0
 0%
     -homebound group; concentration subscale
 5
 7
 15
 22.4
 0
 0%
Shortened Fatigue Questionnaire
 van der Werf et al. [22]
     -survey respondents (Dutch ME-Association members)
 4
 7
 1955
 23.9
 0
 0%
     -research participants (CDC94-UCF)
 4
 7
 270
 26.1
 567
 53%
Shortened Fatigue Questionnaire
 Oxford-CFS, CDC94-UCF; Alberts et al. [11]
     -normative data for CFS
 4
 7
 445
 26 to 27
 890
 50%
Shortened Fatigue Questionnaire
 CDC94-CFS; Vermeulen et al. [12]
     -study group
 4
 7
 35
 24.8
 28
 20%
Krupp Fatigue Severity Scale
 CDC88-CFS; Friedberg et al. [19]
     -treatment group
 9
 7
 22
 58
 88
 44%
     -no-treatment group
 9
 7
 22
 51
 0
 0%
Krupp Fatigue Severity Scale
 CDC88-CFS; DeLuca et al. [23]
     -subjects with concurrent axis 1 psychiatric disorder
 9
 7
 12
 58.5
 54
 50%
     -subjects without concurrent psychiatric disorder
 9
 7
 21
 57.2
 67
 36%
14-item Chalder Fatigue Scale
 Oxford-CFS; Wearden et al. [15]
     -'exercise and fluoxetine group'
 14
 3
 33
 35.9
 261
 56%
     -'exercise and placebo group'
 14
 3
 34
 33.7
 194
 41%
     -'exercise control and fluoxetine group'
 14
 3
 35
 34.4
 224
 46%
     -'exercise control and placebo group'
 14
 3
 34
 34.0
 204
 43%
14-item Chalder Fatigue Scale
 Oxford-CFS; Fulcher et al. [16]
     -exercise group
 14
 3
 33
 28.9
 30
 6%
     -fiexibility group
 14
 3
 33
 30.5
 83
 18%
11-item Chalder Fatigue Scale
 CDC94-CFS; Jason et al. [13]
     -physical subscale
 7
 3
 15
 18.40
 66
 63%
     -mental subscale
 4
 3
 15
 9.13
 17
 28%
11-item Chalder Fatigue Scale
 CDC94-CFS; Wallman et al. [17]
     -exercise group; physical subscale
 7
 3
 32
 11.6
 0
 0%
     -exercise group; mental subscale
 4
 3
 32
 6.3
 0
 0%
     -relaxation/flexibility group; physical subscale
 7
 3
 29
 11.4
 0
 0%
     -relaxation/flexibility group; mental subscale
 4
 3
 29
 5.6
 0
 0%
11-item bimodal Chalder Fatigue Scale
 Oxford-CFS and CDC94-CFS; Deale et al. [20]
     -cognitive behavior therapy group
 11
 1
 30
 10.1
 303
 92%
     -relaxation group
 11
 1
 30
 9.3
 279
 85%
11-item bimodal Chalder Fatigue Scale
 Oxford-CFS; Powell et al. [18]
     -control group
 11
 1
 34
 10.6
 360
 96%
     -minimum intervention group
 11
 1
 37
 10.4
 385
 95%
     -telephone intervention group
 11
 1
 39
 9.9
 386
 90%
     -maximum intervention group
 11
 1
 38
 10.2
 388
 93%

Stouten BMC Health Services Research 2005 5:37   doi:10.1186/1472-6963-5-37