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. 2020 Aug 17;117(35):21209–21217. doi: 10.1073/pnas.2004535117

Table 4.

GAMM of the association between preceding amount of social activity and future sleepiness at different times of day

Variable Estimate SE t-value P value
Parametric coefficients
 Intercept −0.48 0.04 −12.88 <0.001
 Workday 0.47 0.05 9.51 <0.001
Smooth terms EDF RefDF F-value
 Social activity [workday] 0.00 4 0 1.00
 Social activity [freeday] 0.00 4 0 0.993
 Time of day 2.97 3 472.20 <0.001
 Social activity × time of day [workday] 4.83 12 13.94 <0.001
 Social activity × time of day [freeday] 5.46 12 4.78 <0.001
 Random intercept for participant 161.80 462 0.60 <0.001

GAMM, generalized additive mixed-effect model; EDF, effective degrees of freedom; RefDF, reference degrees of freedom. Smooth terms with categorical moderators, as specified in square brackets, represent separate smoothing terms given the moderator’s condition. An “x” between two variables represents a continuous interaction. All smooth terms are centered at zero. P values for smooth terms represent a test of whether the term is different to a flat line.