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What is the difference between robust and cluster?
Robust standard errors are generally larger than non-robust standard errors, but are sometimes smaller. Clustered standard errors are a special kind of robust standard errors that account for heteroskedasticity across “clusters” of observations (such as states, schools, or individuals).
What is the robust option in Stata?
robust is a programmer’s command that computes a robust variance estimator based on varlist of equation-level scores and a covariance matrix.
What does VCE stand for Stata?
variance–covariance matrix of the estimators
VCE stands for variance–covariance matrix of the estimators. The standard errors that sem and gsem report are the square roots of the diagonal elements of the VCE. vce(oim) is the default. oim stands for observed information matrix (OIM).
What does VCE robust do in Stata?
vce(robust) uses the robust or sandwich estimator of variance. This estimator is robust to some types of misspecification so long as the observations are independent; see [U] 20.21 Obtaining robust variance estimates.
What does Areg do in Stata?
areg identifies the model by choosing the intercept that makes the prediction calculated at the means of the independent variables equal to the mean of the dependent variable: y = x ̂β.
Is there an unclustered VCE estimator in Stata?
So the fact that you got the same results with the second and third is not at all surprising. You cannot get an unclustered -xtreg, vce (robust)- in Stata: it is not implemented, because it is not a valid vce estimator.
Which is the robust cluster estimator in Stata?
Let’s consider the following three estimators available with the regress command: the ordinary least squares (OLS) estimator, the robust estimator obtained when the vce (robust) option is specified (without the vce (cluster clustvar) option), and the robust cluster estimator obtained when the vce (cluster clustvar) option is specified.
What are the options in the Stata object?
Each piece can have a Stata object followed by some options; note the commas before optlist (Robust) and before vce (`vce’). In the case at hand, the second piece only contains what the user specified – vce (robust) – and the first piece only contains the options optlist (Robust) and argoptlist (CLuster).
When to use the optional multiplier in Stata?
When the optional multiplier obtained by specifying the hc2 option is used, then the expected values are equal; indeed, the hc2 multiplier was constructed so that this would be true. For more information on these multipliers, see example 6 and the Methods and Formulas section in [R] regress .