. Author manuscript; available in PMC: 2006 Aug 4.

Published in final edited form as: Dev Psychol. 1998 May;34(3):565–573. doi: 10.1037//0012-1649.34.3.565

Table 3.

Direct Effects of Determinants of Mental Development Index (MDI) and Psychomotor Development Index (PDI) Scores

	8-monthMDI		18-month MDI		ΔMDI		8-month PDI
Step and variable	R² (Added)	β	R² (Added)	β	R² (Added)	β	R² (Added)	β
Step 1
Group	.00	0.00	.05^*	-0.22^*	.04^*	-0.19^*	.11^***	-.34^***
Step 2
Alcohol		0.06		-0.01		0.03		-0.09
Cigarettes		0.03		-0.01		-0.03		-0.14
Marijuana	.00	0.00	.01	0.08	.01	0.07	.02	-0.07
Step 3
Medical risk	.00	-0.01	.03	-0.19	.02	-0.16	.00	0.06
Step 4
Environmental risk	.06^*	-0.25^*	.04^*	-0.20^*	.00	-0.04	.02	-0.13
Step 5
Group × Environmental risk	.02	-0.79	.02	0.88	.04^*	1.19^*	.01	0.48
Total R ²	.08		.14^*		.11		.17^**

p < .05.

^**

p < .01.

^***

p < .001.