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. 2021 Sep 23;3(4):515–527. doi: 10.3390/clockssleep3040036

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© 2021 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Agreement between Zulu Watch and Diary Measures of Sleep Timing and Duration. (a) Bland-Altman plots of the differences (y-axis) between the Zulu watch and diary measures of sleep versus the mean of the two measurements (x-axis). Bias is represented by the solid line (―). Upper and lower limits of agreement (LOAs) are represented by the dashed lines (- -). Narrower LOAs indicate relatively less variability between measures. Agreement is shown for (a) Zulu watch and diary measures of sleep duration (●); (b) Zulu watch TST and diary sleep duration (◦) (c) time of sleep onset (▲); (d) time of final awakening (Δ).

Agreement between Zulu Watch and Diary Measures of Sleep Timing and Duration. (a) Bland-Altman plots of the differences (y-axis) between the Zulu watch and diary measures of sleep versus the mean of the two measurements (x-axis). Bias is represented by the solid line (―). Upper and lower limits of agreement (LOAs) are represented by the dashed lines (- -). Narrower LOAs indicate relatively less variability between measures. Agreement is shown for (a) Zulu watch and diary measures of sleep duration (●); (b) Zulu watch TST and diary sleep duration (◦) (c) time of sleep onset (▲); (d) time of final awakening (Δ).