Table 2

Tests of scaling assumptions
Scale
 # items per
scale, k
 (a) Item internal consistency
 (b) Item discriminant validity




Rangea
 Comparisonb
 Success rate (%)
 Rangec
 Comparisond
 Success rate (%)
PF
 10
 0.48 – 0.68
 10/10
 100
 0.10 – 0.31
 70/70
 100
RP
 4
 0.65 – 0.77
 4/4
 100
 0.18 – 0.44
 28/28
 100
BP
 2
 0.83
 2/2
 100
 0.22 – 0.46
 14/14
 100
GH
 5
 0.60 – 0.79
 5/5
 100
 0.14 – 0.45
 35/35
 100
VT
 4
 0.64 – 0.75
 4/4
 100
 0.16 – 0.59
 28/28
 100
SF
 2
 0.77
 2/2
 100
 0.20 – 0.40
 14/14
 100
RE
 3
 0.67 – 0.84
 3/3
 100
 0.18 – 0.44
 21/21
 100
MH
 5
 0.50 – 0.75
 5/5
 100
 0.12 – 0.66
 35/35
 100

a Correlations between items and hypothesized scale, corrected for overlap

b Number of items out of k with correlation ≥ 0.40

c Correlations between items and other scales

d Number of items out of 7 × k where difference between the correlation of the item with its own scale and correlation with the other scales ≥ 2SE (= 0.0576)

Lim et al. Health and Quality of Life Outcomes 2008 6:52   doi:10.1186/1477-7525-6-52