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. Author manuscript; available in PMC: 2019 Jul 1.
Published in final edited form as: Am J Phys Anthropol. 2018 Jul;166(3):590–600. doi: 10.1002/ajpa.23454

Figure 1.

Figure 1

Variation in sleep onset is shown as a function of the number of nights of sleep recorded for each participant (best fit line y = 25.2 + 4.7*x). The profile of sleep recording lengths is bi-modally distributed around 3 nights and 7 nights, which is insufficient to test for a non-linear relationship. However, since a significant linear relationship was found, we include “number of nights recorded” as a control variable.