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Table 6 Descriptive Statistics of the Total Sample, Test of Gender Differences, Bivariate Correlations Between Individual ISI Items, and Item-Total Correlations Among Male and Female Adult Workers

From: Validation of the German version of the insomnia severity index in adolescents, young adults and adult workers: results from three cross-sectional studies

  M SD Range Skew Kurt Gender differences
ANOVA Chi2-test
Descriptive statistics       F η2 Chi2 ϕ
Item 1 0.70 0.93 0-4 1.27 0.95 2.70 .005   
Item 2 1.09 1.15 0-4 0.93 0.09 0.05 .000 --- ---
Item 3 0.99 1.11 0-4 0.94 −0.01 0.40 .001 --- ---
Item 4 1.41 1.07 0-4 0.55 −0.40 0.09 .000 --- ---
Item 5 1.23 0.95 0-4 0.58 −0.18 0.34 .001 --- ---
Item 6 0.89 0.92 0-4 0.80 −0.17 0.38 .001 --- ---
Item 7 0.67 1.01 0-4 1.52 1.56 0.00 .000 --- ---
ISI total score 6.98 4.96 0-26 1.02 0.92 0.01 .000 0.48 .030
Bivariate correlations Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 rit
Item 1 --- .40*** .32*** .51*** .20*** .12* .49*** .49***
Item 2 .56*** --- .72*** .71*** .23*** .13* .66*** .72***
Item 3 44*** .57*** --- .62*** .20*** .11* .61*** .65***
Item 4 .63*** .73*** .51*** --- .19*** .06 .70*** .70***
Item 5 .20* .15 .22* .19* --- .45*** .30*** .35***
Item 6 .12 .06 .05 .12 .41*** --- .27*** .25***
Item 7 .62*** .66*** .54*** .75*** .40*** .22* --- .77***
rit .64*** .68*** .57*** .73*** .34*** .21* .68*** ---
  1. Correlations for male participants are listed below the diagonal, correlations for girls above the diagonal. Item 1 = Difficulty falling asleep; Item 2 = Difficulty staying asleep; Item 3 = Waking up too early; Item 4 = How satisfied are you with your current sleep pattern?; Item 5 = To what extent do you consider your sleep problem to interfere with your daily functioning (e.g., daytime fatigue, ability to function at work/daily chores, concentration, memory, mood, etc.)?; Item 6 = How noticeable to others do you think your sleeping problem is in terms of impairing the quality of your life?; Item 7 = How worried/distressed are you about your current sleep problem?
  2. *p < .05, ***p < .001