Table 4 Reliability, floor, ceiling effect, and measurement error of the Insomnia Severity Index Danish version (n = 163)
From: Preliminary validation of the insomnia severity index in Danish outpatients with a medical condition
Floor effects, n [%] | 11 [4.4] |
Ceiling effects, n [%] | 0 [0.0] |
Reliability | |
Internal consistency, Cronbach’s alpha [inter-item correlation range] | |
Global scale (all 7 scale items) | 0.90 [0.52–0.80] |
Model 2 | |
Severity subscale (item 1, 2, 3, 4) | 0.83 [0.74–0.88] |
Impact subscale (item 5, 6, 7) | 0.88 [0.85–0.92] |
Model 4 | |
Severity subscale (item 1, 2, 3) | 0.75 [0.38–0.55] |
Dissatisfaction subscale (item 1, 4, 7) | 0.81 [0.50–.072] |
Impact subscale (item 5, 6, 7) | 0.88 [0.63–0.79] |
Test-retest reliability | |
ICC [95%CI] | 0.90 [0.87–0.93] |
Measurement error | |
SEM (\( \sqrt{mean} square(ANOVA) \)) | 2.52 |
SDC (1.96 × √ 2 × SEM) | 6.99 |
LoA (mean difference between test and retest) [95% limits] | 0.05 [−6.92–7.02] |