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What is the meaning of robust standard error?
“Robust” standard errors is a technique to obtain unbiased standard errors of OLS coefficients under heteroscedasticity. “Robust” standard errors have many labels that essentially refer all the same thing. Namely, standard errors that are computed with the sandwich estimator of variance.
Should I use robust standard error?
Thus, it is safe to use the robust standard errors (especially when you have a large sample size.) Even if there is no heteroskedasticity, the robust standard errors will become just conventional OLS standard errors. Thus, the robust standard errors are appropriate even under homoskedasticity.
Why are cluster robust standard errors larger?
In such DiD examples with panel data, the cluster-robust standard errors can be much larger than the default because both the regressor of interest and the errors are highly correlated within cluster. This serial correlation leads to a potentially large difference between cluster-robust and default standard errors.
What’s the difference between robust and clustered standard errors?
-xtreg- with fixed effects and the -vce (robust)- option will automatically give standard errors clustered at the id level, whereas -areg- with -vce (robust)- gives the non-clustered robust standard errors. The latter seems to be what Wooldridge estimated.
Do you use cluster standard errors in fixed effects model?
However, HC standard errors are inconsistent for the fixed effects model. Therefore, it is the norm and what everyone should do to use cluster standard errors as oppose to some sandwich estimator.
Which is the correct estimator for fixed effects?
In the case of fixed effects models, one should note that the coefficients can be estimated through the within estimator ( xtreg or LSDV: reg y x i.pid ). The asymptotic standard errors are correct for the LSDV and and for the within after correcting the degree of freedom (which all implementations should do).
Which is the robust standard error estimator in Stata?
These are known as CRVE or cluster robust Variance-Covariance estimators. Stata xtreg and xtivreg and similar commands are for short-panels one-way error models (one can include the temporal intercept for two-way error models manually).