Table 4.

Reliability and validity results of the candidate short forms

Form Length	Cronbach’s alpha (95% CI)	Correlation of summed scores (95% CI)	Correlation of factor scores (95% CI)
Item 9 Eligible for Inclusion in Short Forms
1	NA	0.527 (0.511, 0.543)	NA
2	0.533 (0.504, 0.563)	0.804 (0.796, 0.811)	0.800 (0.792, 0.808)
3	0.727 (0.712, 0.741)	0.863 (0.857, 0.868)	0.869 (0.863, 0.874)
4	0.801 (0.790, 0.810)	0.892 (0.887, 0.896)	0.895 (0.890, 0.899)
5	0.809 (0.799, 0.819)	0.920 (0.916, 0.923)	0.912 (0.909, 0.916)
6	0.835 (0.826, 0.843)	0.939 (0.937, 0.942)	0.931 (0.928, 0.934)
7	0.846 (0.839, 0.854)	0.971 (0.970, 0.973)	0.980 (0.979, 0.980)
8	0.858 (0.851, 0.865)	0.986 (0.986, 0.987)	0.989 (0.989, 0.990)
9	0.866 (0.860, 0.873)	1.000 (1.000, 1.000)	1.000 (1.000, 1.000)
Item 9 Ineligible for Inclusion in Short Forms
1	NA	0.781 (0.772, 0.79)	NA
2	0.779 (0.763, 0.794)	0.849 (0.842, 0.855)	0.860 (0.855, 0.866)
3	0.816 (0.806, 0.826)	0.887 (0.882, 0.892)	0.891 (0.886, 0.895)
4	0.805 (0.795, 0.814)	0.919 (0.916, 0.923)	0.910 (0.907, 0.914)
5	0.832 (0.824, 0.840)	0.940 (0.936, 0.941)	0.930 (0.927, 0.933)
6	0.845 (0.838, 0.852)	0.970 (0.969, 0.971)	0.978 (0.977, 0.979)
7	0.857 (0.850, 0.863)	0.984 (0.984, 0.985)	0.988 (0.987, 0.988)
8	0.866 (0.860, 0.872)	0.997 (0.997, 0.997)	0.998 (0.998, 0.998)

Bold values represent those of the final selected form.