highly significantp < .01
For sleep parameters (see Table 4 ), differences between the null models and the main and interaction models proved to be insignificant for quality, χ 2 (6) = 2.15, p = .906, and highly significant for duration, χ 2 (6) = 18.61, p < .01), and onset latency, χ 2 (6) = 36.28, p < .001.