. Author manuscript; available in PMC: 2019 Mar 11.

Published in final edited form as: Am Econ J Appl Econ. 2018 Jan;10(1):307–341. doi: 10.1257/app.20160404

Appendix Table 4.

Hausman Tests for the Equivalence of OLS and IV Estimates

	OLS (1)	IV1 (2)	IV2 (3)
Single random draw of blood lead levels	−0.186 [0.0188]	−0.442 [0.0372]	−0.924 [0.426]
Observations	54,491	54,491	54,491
R²	0.233
Instrument	None	Average of other BLLs	Predicted certificate
Hausman test (chi squared) comparing OLS and IV estimates		12.1	0.53

Notes: Sample restricted to children with at least two BLLs. Also included are all covariates listed in Table 3A, column 3, whether the home has/will ever receive a certificate, year of birth and month of birth, and census tract fixed effects. The null hypothesis for the Hausman test is that the difference in the coefficients is not systematic. The test statistics indicate that the IV1 and OLS coefficients are different, but that the IV2 and OLS coefficients are not.