Table 4.

Treatment effects on IQ z-score by low-income status using IHDP HLBW sample with ECLS-B weights.

Outcome (sample size)		Model
		A	B	C
Age 1 IQ (n=330)	Treatment	0.109 (0.132)	0.112 (0.133)	0.065 (0.177)
	Low income		−0.037 (0.122)	−0.072 (0.171)
	Treatment x (low income)			0.097 (0.253)
Age 2 IQ (n=322)	Treatment	0.793*** (0.160)	0.878*** (0.223)	0.433* (0.219)
	Low income		−0.875*** (0.244)	−1.181*** (0.270)
	Treatment x (low income)			0.872** (0.280)
Age 3 IQ (n=328)	Treatment	0.903*** (0.147)	1.001*** (0.181)	0.323 (0.210)
	Low income		−1.017*** (0.192)	−1.482*** (0.240)
	Treatment x (low income)			1.319*** (0.308)
Age 5 IQ (n=295)	Treatment	0.102 (0.116)	0.148 (0.166)	−0.264 (0.201)
	Low income		−0.509* (0.246)	−0.820*** (0.231)
	Treatment x (low income)			0.861*** (0.201)
Age 8 IQ (n=311)	Treatment	0.156 (0.158)	0.224 (0.169)	−0.067 (0.323)
	Low income		−0.595** (0.185)	−0.806*** (0.196)
	Treatment x (low income)			0.572 (0.361)

Coefficient significance (within site correlation corrected standard errors):

^*0.10

^**0.05

^***0.01. All models also condition on child gender, birth weight, gestational age at birth, neonatal health index, and site indicators. Estimates in appendix.