Table 3.

Average (and SD) of each of the median groups for relevant acoustic correlates, as well as the outcome measure. The first two columns show peak location for the sibilants in kilohertz and the following two columns show measures of distance between the two categories within each talker’s speech: D(a) (distance between the means divided by the average variance) and Welch’s t (distance between the means divided by frequency-weighted variance); the fifth rightmost column displays the outcome of discrimination scores. These averages are given for the whole sample (overall) and also separating infants in their age groups; in the last line of each of these three groupings is the t-value of an unequal variance, two-tailed test across the two median groups is shown together with its significance level (***p < 0.001; **p < 0.01; *p < 0.05).

	Median group	Peak location				Inter-category distance				Discrimination
	∕s/		∕∫∕		D(a)		Welch’s t		scores
Overall	L	6.531	(0.624)	3.622	(0.313)	1.57	(0.51)	7.61	(0.094)	0.504	(0.094)
	H	8.28	(0.876)	4.135	(0.736)	2.61	(0.736)	11.91	(0.75)	0.568	(0.098)
	t across groups	7.453	***	2.934	**	5.29	***	4.20	***	2.17	*
4-6 months	L	6.422	(0.594)	3.591	(0.359)	1.51	(0.359)	7.20	(1.97)	0.524	(1.97)
	H	8.391	(1.212)	4.576	(0.962)	2.35	(0.93)	10.07	(3.12)	0.572	(0.064)
	t across groups	4.003	**	2.598	*	2.28		2.18		1.491
12-14 months	L	6.651	(0.665)	3.657	(0.268)	1.63	(0.268)	8.07	(3.90)	0.482	(0.114)
	H	8.224	(0.701)	3.914	(0.499)	2.74	(0.64)	12.82	(3.56)	0.566	(0.113)
	t across groups	5.583	***	1.623		4.23	***	3.05	**	1.792