Table 4.

Word intelligibility score (%) and Longest utterance (count) versus Time since onset of single word productions and Age at first single word production

Word Intelligibility (%)	Estimate	Std. Error	Df	t value	Pr(>|t|)
(Intercept)	12.83	4.91	17.7	2.61	0.017810
Time (months) since single word production	1.10	0.32	30.8	3.42	0.001784
Age at first single word production (months)1*	−0.34	0.56	16.7	−0.60	0.554200
Time × Age*	−0.07	0.03	21.3	−2.11	0.046970

Longest Utterance (count)	Estimate	Std. Error	df	t value	Pr(>|t|)
(Intercept)	1.47	0.30	28.6	4.87	0.0000375
Time (months) since single word production	0.10	0.03	53.5	3.76	0.0004257
Age at first single word production (months)1**	0.04	0.03	23.2	1.26	0.2186000
Time × Age**	−0.008	0.00	50.6	−3.21	0.0023160

^*Simultaneous test of Age at first single word production and Time × Age: F=4.30 (2 df), p=0.018.

¹Age at first single word production was centered at age=36 months.

^**Simultaneous test of Age at first single word production and Time × Age: F=5.72 (2 df), p=0.005.

¹Age at first single word production was centered at age=36 months.