Table 3

Subject functional ability and item difficulty levels, reliability indices and principal component analysis of the standardised residuals for each of the three ALSFRS-R subscales

Subscale 1 (item 1–3)Subscale 2 (item 4–9)Subscale 3 (item 10–12)
Average subject functional ability levels (range)0.39 (−5.91 to 5.91)−0.74 (−5.50 to 5.60)0.90 (−6.17 to 6.08)
Item difficulty levels (range)−1.09 to 0.80−1.24 to 1.80−2.03 to 1.81
Person separation reliability0.780.820.69
Cronbach's α0.880.910.82
Variance explained by the Rasch factor (%)55.459.260.6
Eigenvalue of the first residual factor1.62.41.5
  • ALSFRS-R, Amyotrophic Lateral Sclerosis Functional Rating Scale-revised.