. Author manuscript; available in PMC: 2011 Nov 4.

Published in final edited form as: Dev Psychol. 2008 Nov;44(6):1557–1571. doi: 10.1037/a0013913

Table 2. Sample Sizes by Child's Age at Baseline (in Years) and Outcome Measure.

	Age at baseline(in years)

Unit of analysis	Under 1^a	1	2	3	Total
Achievement
Observations^b	204	1,781	2,707	3,062	7,754
Children	171	1,183	1,926	1,945	5,223
Families	169	1,161	1,903	1,908	4,580^c

Positive social behavior
Observations^b	157	1,382	2,011	1,841	5,391
Children	132	942	1,515	1,381	3,969
Families	132	932	1,509	1,369	3,698^c

Problem behavior
Observations^b	158	1,387	2,017	1,853	5,415
Children	132	942	1,515	1,386	3,974
Families	132	932	1,509	1,374	3,705^c

This category includes children 6–11 months in age at random assignment. There were insufficient numbers of children under 6 months to include in these analyses.

There were multiple observations per child if the study either measured outcomes at two follow-up points or collected multiple measures of achievement (from parent, teacher, and test) per child.

This row does not sum to the total because some families contributed children in multiple age groups.