Background
-
Our second hypothesis was that the ISI would have adequate homogeneity and internal consistency across all study populations, and both males and females [9, 17, 19, 21‐23]. More specifically, we expected inter-item correlations ≥ .20, Cronbach’s alpha coefficients ≥ .70, and item-total correlations ≥ .30 [38].
-
Our third hypothesis was that adequate convergent validity would exist in male and female participants across all study populations. That is, we hypothesized that the individual items and the total ISI score would be at least moderately and positively correlated with the corresponding items of the PSQI [17, 19, 23].
-
With regard to factorial validity, we did not have a clear-cut hypothesis. Nevertheless, we expected that adequate model fit would be found with either a 1-, 2- or 3-factor model [17, 22]. For the best fitting model, we assumed fair factor loadings on the corresponding factors (≥ .45) [39], and at least weak measurement invariance across genders (see methods of study 1 for more information regarding types of measurement invariance).
Study 1
Methods
Participants and procedures
Sleep
Psychological functioning
Statistical analyses
Results
M | SD | Range | Skew | Kurt | Gender differences | ||||
---|---|---|---|---|---|---|---|---|---|
ANOVA | Chi2-test | ||||||||
Descriptive statistics | F | η2 | Chi2 | ϕ | |||||
Item 1 | 1.07 | 1.02 | 0-4 | 0.77 | 0.05 | 20.46*** | .014 | --- | --- |
Item 2 | 0.65 | 0.97 | 0-4 | 1.51 | 1.60 | 7.40** | .005 | --- | --- |
Item 3 | 0.92 | 1.16 | 0-4 | 1.12 | 0.27 | 6.74* | .005 | --- | --- |
Item 4 | 1.03 | 0.96 | 0-4 | 0.94 | 0.50 | 25.80*** | .017 | --- | --- |
Item 5 | 1.25 | 0.88 | 0-4 | 0.56 | 0.19 | 6.96** | .005 | --- | --- |
Item 6 | 1.14 | 0.97 | 0-4 | 0.84 | 0.46 | 3.44 | .002 | --- | --- |
Item 7 | 0.61 | 0.89 | 0-4 | 1.61 | 2.43 | 11.40** | .008 | --- | --- |
ISI total score | 6.67 | 4.39 | 0-27 | 1.00 | 1.13 | 25.91*** | .017 | 21.02*** | .12 |
Bivariate correlations | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | rit | |
Item 1 | --- | .43*** | .27*** | .58*** | .25*** | .17*** | .39*** | .55*** | |
Item 2 | .39** | --- | .47*** | .53*** | .17*** | .11** | .34*** | .55*** | |
Item 3 | .25*** | .43*** | --- | .36*** | .13*** | .12** | .28*** | .42*** | |
Item 4 | .53*** | .51*** | .36*** | --- | .25*** | .14*** | .50*** | .63*** | |
Item 5 | .23*** | .24*** | .16*** | .34*** | --- | .47*** | .30*** | .39*** | |
Item 6 | .15*** | .14*** | .11** | .20*** | .46*** | --- | .17*** | .28*** | |
Item 7 | .42*** | .34*** | .25*** | .48*** | .33*** | .27*** | --- | .52*** | |
rit | .50*** | .54*** | .39*** | .64*** | .44*** | .32*** | .54*** | --- |
Males | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Total |
Sleep
| ||||||||
SOL (min) | .42*** | .27*** | .17*** | .27*** | .13** | .08* | .17*** |
.38***
|
Awakenings | .27*** |
.36***
| .24*** | .32*** | .19*** | .08* | .24*** |
.34***
|
Sleep duration (h) | -.12** | -.04 |
.01
| -.13*** | -.02 | -.08* | -.10** |
-.10**
|
MR: Sleep quality | .54*** | .46*** | .34*** |
.71***
| .38*** | .23*** | .54*** |
.71***
|
MR: Restoration | .37*** | .28*** | .21*** | .55*** |
.35***
|
.29***
|
.41***
|
.54***
|
MR: Mood | .26*** | .24*** | .15*** | .38*** |
.30***
|
.27***
|
.22***
|
.40***
|
DR: Sleepiness | .33*** | .28*** | .15*** | .37*** |
.35***
|
.26***
|
.31***
|
.45***
|
DR: Concentration | .34*** | .33*** | .34*** | .48*** |
.36***
|
.26***
|
.38***
|
.55***
|
ER: Sleepiness | -.01 | .07 | -.03 | .03 | .16*** | .09* | .07 |
.08*
|
ER: Mood | .23*** | .21*** | .21*** | .23*** | .12** | .09* | .17*** |
.28***
|
Psychological functioning
| ||||||||
KIDSCREEN | -.30*** | -.29*** | -.23*** | -.40*** | -.23* | -.11 | -.32*** |
-.38***
|
Females | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Total |
Sleep
| ||||||||
SOL (min) |
.47***
| .27*** | .22*** | .40*** | .19*** | .09* | .31*** |
.44***
|
Awakenings | .26*** |
.49***
| .30*** | .32*** | .13*** | .05 | .28*** |
.41***
|
Sleep duration (h) | -.10* | -.11** |
.04
| -.18*** | -.11** | -.13*** | -.08* |
-.17***
|
MR: Sleep quality | .60*** | .58*** | .41*** |
.74***
| .26*** | .22*** | .49*** |
.74***
|
MR: Restoration | .47*** | .38*** | .22*** | .58*** |
.37***
|
.27***
|
.40***
|
.60***
|
MR: Mood | .32*** | .24*** | .13** | .31*** |
.32***
|
.33***
|
.22***
|
.41***
|
DR: Sleepiness | .37*** | .36*** | .23*** | .39*** |
.43***
|
.32***
|
.35***
|
.54***
|
DR: Concentration | .37*** | .35*** | .28*** | .44*** |
.33***
|
.23***
|
.37***
|
.53***
|
ER: Sleepiness | -.12** | .01 | .00 | .00 | .12** | .15*** | .05 |
.04
|
ER: Mood | .27*** | .24*** | .21*** | .28*** | .13*** | .09** | .21*** |
.33***
|
Psychological functioning
| ||||||||
KIDSCREEN | -.37*** | -.36*** | -.26*** | -.44*** | -.28*** | -.25*** | -.34*** |
-.51***
|
Study 1 | CFI | TLI | NFI | PClose | RMSEA | p(Δχ2) |
1-Factor Modela | ||||||
Default model | 0.98 | 0.96 | 0.98 | 0.94 | .04 (.03, .05) | --- |
+ Configural invariance across genders | 0.98 | 0.96 | 0.97 | 0.96 | .04 (.03, .05) | .084 |
+ Weak invariance across genders | 0.98 | 0.97 | 0.97 | 0.99 | .04 (.03, .05) | .284 |
+ Strong invariance across genders | --- | --- | --- | --- | --- | .000 |
+ Strict invariance across genders | --- | --- | --- | --- | --- | --- |
Study 2 | CFI | TLI | NFI | PClose | RMSEA | p(Δχ2) |
1-Factor Model1 | ||||||
Default model | 1.00 | 1.00 | 1.00 | 1.00 | .00 (.00, .03) | --- |
+ Configural invariance across genders | 1.00 | 1.00 | 1.00 | 1.00 | .01 (.00, .03) | .072 |
+ Weak invariance across genders | 1.00 | 1.00 | 1.00 | 1.00 | .02 (.00, .04) | .058 |
+ Strong invariance across genders | 1.00 | 1.00 | 1.00 | 1.00 | .02 (.00, .04) | .124 |
+ Strict invariance across genders | --- | --- | --- | --- | --- | .003 |
Study 3 | CFI | TLI | NFI | PClose | RMSEA | p(Δχ2) |
1-Factor Modela | ||||||
Default model | 1.00 | 1.00 | 0.99 | 0.99 | .00 (.00, .04) | --- |
+ Configural invariance across genders | 1.00 | 1.00 | 0.99 | 0.98 | .00 (.00, .04) | .121 |
+ Weak invariance across genders | 1.00 | 1.00 | 0.98 | 0.98 | .00 (.00, .04) | .116 |
+ Strong invariance across genders | 1.00 | 1.00 | 0.98 | 1.00 | .00 (.00, .04) | .855 |
+ Strict invariance across genders | 1.00 | 1.00 | 0.97 | 1.00 | .00 (.00, .04) | .417 |
Study 2
Methods
Participants and procedures
Sleep
Psychological functioning
Statistical analyses
Results
M | SD | Range | Skew | Kurt | Gender differences | ||||
---|---|---|---|---|---|---|---|---|---|
ANOVA | Chi2-test | ||||||||
Descriptive statistics | F | η2 | Chi2 | ϕ | |||||
Item 1 | 0.67 | 0.93 | 0-4 | 1.45 | 1.76 | 5.67* | .007 | --- | --- |
Item 2 | 0.66 | 0.92 | 0-4 | 1.47 | 1.80 | 9.46** | .011 | --- | --- |
Item 3 | 0.49 | 0.86 | 0-4 | 1.90 | 3.13 | 0.95 | .001 | --- | --- |
Item 4 | 1.09 | 1.04 | 0-4 | 0.82 | 0.03 | 2.61 | .003 | --- | --- |
Item 5 | 1.71 | 1.01 | 0-4 | 0.28 | −0.57 | 1.63 | .002 | --- | --- |
Item 6 | 1.38 | 1.01 | 0-4 | 0.34 | −0.56 | 1.79 | .002 | --- | --- |
Item 7 | 0.57 | 0.91 | 0-4 | 1.57 | 1.64 | 1.48 | .002 | --- | --- |
ISI total score | 6.56 | 4.31 | 0-26 | 1.09 | 1.35 | 6.88** | .008 | 4.67 | .073 |
Bivariate correlations | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | rit | |
Item 1 | --- | .40*** | .20** | .63*** | .19** | .05 | .58*** | .53*** | |
Item 2 | .39*** | --- | .42*** | .59*** | .16* | .11 | .47*** | .55*** | |
Item 3 | .30*** | .48*** | --- | .36*** | .10 | .10 | .29*** | .36*** | |
Item 4 | .67*** | .51*** | .41*** | --- | .22** | .10 | .70*** | .68*** | |
Item 5 | .28*** | .20*** | .17*** | .26*** | --- | .52*** | .29*** | .37*** | |
Item 6 | .06 | .07 | .06 | .09* | .47*** | --- | .15* | .25*** | |
Item 7 | .56*** | .47*** | .32*** | .64*** | .42*** | .25*** | --- | .66*** | |
rit | .57*** | .52*** | .42*** | .65*** | .45*** | .25*** | .69*** | --- |
Males | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Total |
Sleep
| ||||||||
SOL (min) |
.51***
| .11 | .02 | .42*** | .07 | .08 | .32*** |
.34***
|
Awakenings | .34*** |
.57***
| .35*** | .41*** | .15* | .04 | .33*** |
.46***
|
Sleep duration (h) | .13 | -.06 |
-.04
| .10 | .09 | .05 | .10 |
.09
|
MR: Sleep quality | .39*** | .48*** | .24*** |
.55***
| .23** | .06 | .48*** |
.54***
|
MR: Restoration | .41*** | .26*** | .23** | .54*** |
.24**
|
.07
|
.43***
|
.49***
|
MR: Mood | .13 | .05 | -.01 | .18** |
.08
|
.01
|
.18**
|
.14*
|
DR: Sleepiness | .30*** | .26*** | .25*** | .46*** |
.44***
|
.21**
|
.41***
|
.52***
|
DR: Concentration | .36*** | .29*** | .29*** | .47*** |
.43***
|
.10
|
.49***
|
.53***
|
ER: Sleepiness | -.33*** | -.03 | -.01 | -.30*** | -.02 | .02 | -.21 |
-.19***
|
ER: Mood | .12 | .15* | .14* | .26*** | .16* | .10 | .24*** |
.26***
|
Psychological functioning
| ||||||||
Depression scale | .36*** | .35*** | .38*** | .40*** | .31*** | .10 | .43*** |
.50***
|
Females | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Total |
Sleep
| ||||||||
SOL (min) |
.53***
| .25*** | .13** | .43*** | .15*** | .10* | .40*** |
.44***
|
Awakenings | .19*** |
.47***
| .25*** | .38*** | .08 | .11** | .25*** |
.38***
|
Sleep duration (h) | .09*** | -.08 |
-.03
| .06 | .00 | -.03 | -.02 |
.00
|
MR: Sleep quality | .51*** | .51*** | .33*** |
.69***
| .24*** | .12** | .57*** |
.65***
|
MR: Restoration | .46*** | .38*** | .22*** | .54*** |
.25***
|
.14***
|
.53***
|
.56***
|
MR: Mood | .26*** | .18*** | -.04 | 34*** |
.20***
|
.16***
|
.32***
|
.34***
|
DR: Sleepiness | .35*** | .31*** | .21*** | .41*** |
.27***
|
.13***
|
.45***
|
.47***
|
DR: Concentration | .37*** | .34*** | .27*** | .40*** |
.29***
|
.16***
|
.45***
|
.51***
|
ER: Sleepiness | -.15*** | .03 | .02 | -.09* | -.02 | -.03 | -.08 |
-.07
|
ER: Mood | .25*** | .17*** | .13** | .23*** | .04 | .02 | .21*** |
.23***
|
Psychological functioning
| ||||||||
Depression scale | .35*** | .35*** | .27*** | .38*** | .27*** | .19*** | .46*** |
.51***
|
Study 3
Methods
Participants and procedures
Sleep
Psychological functioning
Statistical analyses
Results
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*** | --- |
Males | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Total |
Sleep
| ||||||||
SOL (min) |
.51***
| .27*** | .21*** | .28*** | .10* | .13** | .25*** |
.36***
|
Awakenings | -.18*** |
.52***
| .46*** | .45*** | .18*** | .05 | .37*** |
.47***
|
Sleep duration (h) | -.20*** | -.20*** |
-.20***
| -.27*** | -.04 | -.02 | -.23*** |
-.25***
|
MR: Sleep quality | .48*** | .65*** | .56*** |
.69***
| .28*** | .18*** | .65*** |
.74***
|
MR: Restoration | .40*** | .47*** | .39*** | .56*** |
.36***
|
.23***
|
.53***
|
.61***
|
MR: Mood | .31*** | .30*** | .22*** | .37*** |
.33***
|
.21***
|
.35***
|
.42***
|
DR: Sleepiness | .32*** | .36*** | .34*** | .45*** |
.40***
|
.27***
|
.45***
|
.53***
|
DR: Concentration | .37*** | .42*** | .44*** | .43*** |
.39***
|
.22***
|
.45***
|
.56***
|
ER: Sleepiness | -.07 | .12* | .17** | .06 | .06 | .08 | .10* |
.11*
|
ER: Mood | .26*** | .25*** | .25*** | .29*** | .17*** | .07 | .31*** |
.33***
|
Psychological functioning
| ||||||||
SF12 | -.27*** | -.35*** | -.35*** | -.37*** | -.25*** | -.20*** | -.42*** |
-.46***
|
Females | Item 1 | Item 2 | Item 3 | Item 4 | Item 5 | Item 6 | Item 7 | Total |
Sleep
| ||||||||
SOL (min) |
.28**
| .22* | .21* | .34*** | .06 | .07 | .32*** |
.31***
|
Awakenings | .34*** |
.63***
| .36*** | .55*** | .16 | .03 | .48*** |
.54***
|
Sleep duration (h) | -.25** | -.27** |
-.18*
| -.10 | .04 | .04 | -.11 |
-.18*
|
MR: Sleep quality | .50*** | .63*** | .47*** |
.74***
| .35*** | .13 | .73*** |
.75***
|
MR: Restoration | .37*** | .44*** | .31*** | .62*** |
.29***
|
.20*
|
.58***
|
.59***
|
MR: Mood | .29** | .23* | .27** | .38*** |
.24**
|
.14
|
.34***
|
.39***
|
DR: Sleepiness | .28** | .44*** | .31*** | .46*** |
.36***
|
.11
|
.53***
|
.52***
|
DR: Concentration | .13 | .23* | .31* | .33*** |
.36***
|
.15
|
.33
|
.36***
|
ER: Sleepiness | .13 | .01 | .08 | .01 | .13 | .12 | .06 |
.05
|
ER: Mood | .23** | .25** | .30** | .34*** | .17 | .06 | .33*** |
.33***
|
Psychological functioning
| ||||||||
SF12 | -.22* | -.35* | -.30** | -.45*** | -.27** | -.07 | -.41*** |
-.43***
|