Table 4.

Summary of regression for IQ, hyperactivity, impulsivity, and inattention on Backward Digit Span scores.

	Variable	b	SEb	β	t	R2	R2 change	Semi-partial correlation
Step 1						0.051	0.051∗
	IQ	0.044	0.020	0.225	2.226ˆ*
Step 2						0.066	0.015
	IQ	0.047	0.020	0.237	2.337ˆ*			0.235
	Hyperactivity	-0.024	0.020	-0.124	-1.222			-0.123
Step 3						0.093	0.027
	IQ	0.043	0.020	0.216	2.139ˆ*			0.214
	Hyperactivity	0.012	0.030	0.058	0.391			0.039
	Impulsivity	-0.058	0.035	-0.244	-1.641			-0.164
Step 4						0.218	0.125∗∗
	IQ	0.058	0.019	0.293	3.036ˆ*			0.283
	Hyperactivity	0.047	0.029	0.237	1.606			0.150
	Impulsivity	-0.012	0.035	-0.049	-0.328			-0.031
	Inattention	-0.100	0.026	-0.505	-3.793ˆ*			-0.354

^∗p < 0.05, ^∗∗p < 0.001.