Figure 2. Sleep onset (mean ± SEM) based on actigraphy and sleep diary data (Phase 2) with day of week and availability of electric light as factors (○ with, n = 17, and • without electric light, n = 20).

Electric light F(1, 35) = 4.04, p = 0.05; Day F(1, 35) = 16.93, p < 0.01 and interaction Electric light x Day F(1, 35) = 0.12, p = 0.74. Work day: Monday-Thursday; Day-off: Saturday-Sunday.