Table 3 A summary table of the GAMMs on the pitch values at the six time points of the twelve vowels of all the speakers in Hillenbrand et al. (1995) by the sex and age groups

f0 ~ sex	+ s(Time_Points, k=5)
	+ s(Time_Points, by=sex, k=5)
Parametric coefficients:
		Estimate	Std. Error	t value	Pr(>|t|)
(Intercept)		235.5	0.6	417.63	0.001*
sexGirls		1.7	0.9	1.91	0.056
sexMen		–104.1	0.7	–145.97	0.001*
sexWomen		–15.6	0.7	–22.12	0.001*
Approximate significance of smooth terms:
		edf	Ref.df	F	p-value
s(Time_Points)		2.6	2.8	13.97	0.001*
s(Time_Points):sexGirls		2.4	2.8	11.76	0.001*
s(Time_Points):sexMen		1.0	1.0	21.07	0.001*
s(Time_Points):sexWomen		2.6	2.9	11.88	0.001*
R-sq.(adj)=0.773, Deviance explained=77.4%
fREML= 46,360, Scale est.=618.19, n=10,008, *p<.05