Table 1.
Zero-order correlations and descriptive statistics
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1. Objective Nighttime Sleep Duration (hours) | - | |||||||||||||
| 2. Objective Sleep Midpoint Time | −.19*** | - | ||||||||||||
| 3. Parent-reported Sleep Problems | −.15** | .18** | - | |||||||||||
| 4. Picture Vocabulary | .05 | −.17** | −.16** | - | ||||||||||
| 5. Applied Problems | −.02 | −.04 | −.12* | .54*** | - | |||||||||
| 6. Passage Comprehension | .07 | −.04 | −.11* | .59*** | .61*** | - | ||||||||
| 7. Parent-Reported Academic Achievement | .10 | −.15** | −.15** | .36*** | .44*** | .49*** | - | |||||||
| 8. Early SES | .23*** | −.23*** | −.18** | .27*** | .19*** | .19** | .29*** | - | ||||||
| 9. Concurrent SES | .21*** | −.16** | −.20*** | .34*** | .27*** | .27*** | .31*** | .83*** | - | |||||
| 10. Age (years) | −.23*** | .24*** | .01 | .21*** | .36*** | .33*** | −.05* | −.19** | −.09 | - | ||||
| 11. Race/Ethnicity | .15** | −.19** | −.04 | .16*** | .04 | .13* | .06 | .26*** | .24*** | −.19*** | - | |||
| 12. Sex | .16*** | .04 | .02 | .03 | −.15** | .01 | .01 | −.01 | .05 | .01 | −.05 | - | ||
| 13. BMI | −.18*** | .04 | .05 | −.03 | .02 | −.06 | −.12* | −.16*** | −.12** | .13*** | −.13*** | .02 | - | |
| 14. Vacation | −.01 | .30*** | −.09 | −.06 | −.03 | −.08 | −.03 | −.01 | .05 | −.01 | −.01 | −.02 | .01 | - |
|
| ||||||||||||||
| Mean | 8.12 | 2:13 AM | 1.74 | 483.72 | 483.90 | 476.17 | 3.82 | .00 | .00 | 8.44 | .59 | .52 | 16.76 | .27 |
| Standard Deviation | .73 | 46 min | .35 | 10.15 | 20.30 | 16.44 | .87 | .80 | .81 | .69 | - | - | 2.91 | - |
| Minimum | 4.46 | 12:18 AM | 1.00 | 452.00 | 419.00 | 353.00 | 1.20 | −2.05 | −1.72 | 6.96 | - | - | 12.11 | - |
| Maximum | 10.26 | 4:46 AM | 3.29 | 519.00 | 531.00 | 512.00 | 5.00 | 1.76 | 3.34 | 10.26 | - | - | 34.92 | - |
| Skewness | −.68 | .67 | .71 | −.02 | −.44 | −1.54 | −.41 | −.15 | .54 | −.18 | - | - | 1.99 | - |
| Kurtosis | 1.75 | .57 | .89 | .22 | −.42 | 6.05 | −.55 | −.55 | .42 | −.36 | - | - | 5.92 | - |
Note. N = 707. Sex (1 = female), ethnicity (1 = non-Hispanic White), BMI = body mass index; SES = socioeconomic status. Vacation (1 = study completed during summer or school vacation).
*
p ≤ .05
**
p ≤ .01
***
p ≤ .001.
Parent-reported sleep problems were assessed using the Child Sleep Habits Questionnaire. Parent-reported academic achievement was assessed using the Health and Behavior Questionnaire.