Table 1.
Descriptive statistics of covariates and their relationship with insomnia severity
| M | SD | Min | Max | N | t | r | |
|---|---|---|---|---|---|---|---|
| Covariates | |||||||
| Sex | |||||||
| Female | 328 | − 3.51 (p < .001) | |||||
| Male | 303 | ||||||
| Medication intake | |||||||
| Yes | 253 | 1.76 (p = .08) | |||||
| No | 378 | ||||||
| IQ | |||||||
| IQ < 116 | 240 | − .10 (p = .02) | |||||
| IQ 116–130 | 258 | ||||||
| IQ > 130 | 133 | ||||||
| Age | 42.62 | 12.21 | 18.05 | 64.93 | 631 | − 01 (p = .10) | |
| 18–25 | 21.46 | 2.02 | 18.05 | 24.83 | 60 | .20 (p = .13) | |
| 25–45 | 35.16 | 5.60 | 25.17 | 44.93 | 271 | .12 (p = .19) | |
| 45–65 | 53.51 | 5.29 | 45.01 | 64.93 | 300 | − .15 (p = .01) | |
The influence of sex and medication intake on ISI (insomnia severity index) scores was examined using dependent sample t-tests. The impact of age and intelligence was evaluated by means of Pearson correlations. Variables significant at a level of alpha ≤ .1 were retained and entered as covariates during further analyses