. Author manuscript; available in PMC: 2012 Jul 1.

Published in final edited form as: J Hum Cap. 2011 Summer;5(2):207–254. doi: 10.1086/660885

Table 5.

Effects of Smoking and Number of Cigarettes during Pregnancy on the Child Neurodevelopment Rate^a

Model	Total Sample	Low Socioeconomic Status	High Socioeconomic status
	Smoking participation
OLS	−2.85^** (1.36)	−3.39^** (1.25)	−1.60 (2.28)
2SLS	−29.85 (24.50) [−88.68,24.37]	−37.27^** (19.01) [−85.91, −0.57]	−11.91 (28.75) [−72.82,68.86]
F-statistic [df]	10.3^*** [2, 23]	7.33^** [2, 22]	6.19^*** [2, 23]
Over-identification Chi-square [1]	0.99	0.04	0.19
Exogeneity F-statistic [df]	1.17 [1, 23]	3.26^* [1, 22]	0.12 [1, 23]

	Cigarettes
OLS	−0.25^** (0.11)	−0.26^* (0.13)	−0.22 (0.20)
2SLS	−2.48^** (1.11)	−2.49^** (0.97)	-
Instrument F-statistic [df]	42.1^*** [2,23]	23.96^*** [2, 22]	-
Over-identification Chi-square [1]	0.82	0.33	-
Exogeneity F-statistic [df]	5.62^** [1, 23]	7.23^** [1, 22]	-

Note: Standard errors of effects are in parentheses.

^{*, ** and ***}

indicate p <0.1, <0.05 and <0.01, respectively. 95% Weak-instrument robust confidence bounds for the smoking participation effects are included in brackets.