Table 2.

Participant Developmental Characteristics at 2 and 3 Years

		Total (N = 408)			TD (n = 249)			LT (n = 159)						Cohen’s dc
		M	SD		M	SD		M		SD		t	df
CSBS Caregiver Questionnairea
	Age (months)	19.80	1.59		19.66	1.53		20.04		1.66		2.38*	406	0.24
	Social	9.94	2.95		10.33	2.90		9.33		2.94		3.35**	406	0.32
	Speech	8.85	2.77		10.08	2.64		6.93		1.66		14.80***	406	1.43
	Symbolic	9.03	2.39		9.56	2.28		8.21		2.34		5.79***	406	0.58
CSBS Behavior Samplea
	Age (months)	20.25	1.54		20.13	1.46		20.45		1.64		2.06*	406	0.21
	Social	10.46	3.20		10.86	3.17		9.82		3.17		3.23**	406	0.33
	Speech	8.60	2.46		9.56	2.20		7.11		2.08		11.20***	406	1.14
	Symbolic	10.22	3.01		10.78	2.89		9.35		3.01		4.75***	406	0.49
Language Development Survey
	Age (months)	24.46	0.82		24.49	0.83		24.42		0.79		0.80	406	0.09
	VP	102.20	78.73		145.81	68.55		33.90		29.96		22.60***	406	2.12
	Scaled VP	9.99	2.97		11.64	2.59		7.42		1.13		22.60***	406	2.12
Mullen Scales of Early Learningb
	Age (months)	25.01	0.97		25.02	1.01		25.00		0.89		0.22	406	0.02
	Expressive T	46.02	13.02		52.11	11.34		36.47		9.20		15.27***	406	1.51
	Receptive T	52.62	11.90		55.53	10.73		48.06		12.22		6.31***	406	0.65
		Total (N = 198)			TD (n = 122)			LT (n = 76)
		M	SD		M	SD		M		SD		t	df	d
Mullen Scales of Early Learningb
	Age (months)	37.29	1.95		37.28	2.08		37.25		1.64		0.22	196	0.02
	Expressive T	51.54	13.09		55.33	11.78		45.34		12.49		5.66***	196	0.82
	Receptive T	51.42	11.95		54.74	11.18		45.75		11.11		5.67***	196	0.81

Note. CSBS=Communication and Symbolic Behavior Scales. VP=Vocabulary production.

^aStandard Scores based on M=10, SD=3.

^bT Scores based on M=50, SD=10.

^cEffect size based on Cohen’s d ≥ .20 is small, .50 is medium, and .80 is large (Cohen, 1988).

^*p<.05;

^**p<.01;

^***p<.001.