# [R] Hausman Test

Holger Steinmetz Holger.steinmetz at web.de
Sun Jan 16 15:53:17 CET 2011

```Dear Achim,

thank you very much.

One follow up question. The Hausman-test always gives me a p-value of 1 - no
matter
how small the statistic is.

I now generated orthogonal regressors (X1-X3) and the test gives me

Hausman specification test for consistency of the 3SLS estimation

data:  data
Hausman = -0.0138, df = 2, p-value = 1

What is confusing to me is the "3SLS". I am just beginning to learn about
instrumental variables (I am a psychologist ;) Perhaps that's a problem?

As a background, here's the complete simulation:

W = rnorm(1000)
X2 = rnorm(1000)
X3 = rnorm(1000)
X1 = .5*W  + rnorm(1000)
Y = .4*X1 + .5*X2 + .6*X3 + rnorm(1000)
data = as.data.frame(cbind(X1,X2,X3,Y,W))

fit2sls <- systemfit(Y~X1,data=data,method="2SLS",inst=~W)
fitOLS <- systemfit(Y~X1,data=data,method="OLS")

print(hausman.systemfit(fitOLS, fit2sls))

Best,
Holger
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```