# Questions tagged [heteroskedasticity]

refers to non-constant variance of errors across different observations

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### Showing the unbiased estimator of variance for GLS estimator

I have the following regression $$y = X\beta +u$$ where $y$ and $u$ are $(n\times 1)$ and $X$ is a fixed $(n \times k)$ matrix with full column rank and $\beta$ is an unknown $(k\times 1)$ vector of ...
• 374
1 vote
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### WLS or Feasible GLS?

For a question like this, would I use WLS or Feasible GLS? I am leaning towards WLS but my lecture slides tell me GLS is used when there is more than one variable that drives the residual variance.
1 vote
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1 vote
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### Heteroskedasticity assumption in fGLS into linear form?

I am following Chapter 8 ("Heteroskedasticity" p. 259) in the 6th edition of Woolridge Introductory Econometrics: A Modern Approach and I don't understand one piece of the transformation of our model. ...
• 43
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### Asymptotic variance under heteroskedasticity

I want to find an expression for the asymptotic variance of the OLS estimator given that the errors are heteroskedastic. I have understood the derivation using CLT for the homoskedastic case. I.e., \$...
• 641
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### Heteroscedasticity and weighted least square estimator

"In presence of heteroscedasticity, OLS estimators are unbiased but inefficient" Showing the unbiased part is relatively easy. Some authors have explained the inefficiency with the help of new ... 1 vote
123 views

### possible Heteroskedasticity?

Based on the graph, would you say that there is some sort of heteroscedasticity in the data? Y-axis is residual squared and X-axis is predicted values of Y
• 121
1 vote 