How to find the OLS estimator of variance of error

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Given the Linear Regression model $y=Xbeta+epsilon$, where $epsilon sim D(0_n,sigma^2 I_n)$ and $D$ is some distribution. How to find the OLS estimator of $sigma^2$.



I know that the sum of least-squares residuals has a distribution equal to $sigma^2$ times $chi^2_n-1$. So I can therefore determine the unbiased estimator of $sigma^2$. But how to prove that sum of least-squares residuals follows such distribution. Also anyone with new way to find it are welcome.










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  • In $D(0_n,sigma^2 I_n)$, if $0_n$ is the mean and $sigma^2$ = variance, which kind of distributions meet this condition, apart from normal?
    – a_statistician
    1 hour ago
















up vote
1
down vote

favorite












Given the Linear Regression model $y=Xbeta+epsilon$, where $epsilon sim D(0_n,sigma^2 I_n)$ and $D$ is some distribution. How to find the OLS estimator of $sigma^2$.



I know that the sum of least-squares residuals has a distribution equal to $sigma^2$ times $chi^2_n-1$. So I can therefore determine the unbiased estimator of $sigma^2$. But how to prove that sum of least-squares residuals follows such distribution. Also anyone with new way to find it are welcome.










share|cite|improve this question









New contributor




Sarath is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.



















  • In $D(0_n,sigma^2 I_n)$, if $0_n$ is the mean and $sigma^2$ = variance, which kind of distributions meet this condition, apart from normal?
    – a_statistician
    1 hour ago












up vote
1
down vote

favorite









up vote
1
down vote

favorite











Given the Linear Regression model $y=Xbeta+epsilon$, where $epsilon sim D(0_n,sigma^2 I_n)$ and $D$ is some distribution. How to find the OLS estimator of $sigma^2$.



I know that the sum of least-squares residuals has a distribution equal to $sigma^2$ times $chi^2_n-1$. So I can therefore determine the unbiased estimator of $sigma^2$. But how to prove that sum of least-squares residuals follows such distribution. Also anyone with new way to find it are welcome.










share|cite|improve this question









New contributor




Sarath is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











Given the Linear Regression model $y=Xbeta+epsilon$, where $epsilon sim D(0_n,sigma^2 I_n)$ and $D$ is some distribution. How to find the OLS estimator of $sigma^2$.



I know that the sum of least-squares residuals has a distribution equal to $sigma^2$ times $chi^2_n-1$. So I can therefore determine the unbiased estimator of $sigma^2$. But how to prove that sum of least-squares residuals follows such distribution. Also anyone with new way to find it are welcome.







regression least-squares






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edited 5 hours ago





















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  • In $D(0_n,sigma^2 I_n)$, if $0_n$ is the mean and $sigma^2$ = variance, which kind of distributions meet this condition, apart from normal?
    – a_statistician
    1 hour ago
















  • In $D(0_n,sigma^2 I_n)$, if $0_n$ is the mean and $sigma^2$ = variance, which kind of distributions meet this condition, apart from normal?
    – a_statistician
    1 hour ago















In $D(0_n,sigma^2 I_n)$, if $0_n$ is the mean and $sigma^2$ = variance, which kind of distributions meet this condition, apart from normal?
– a_statistician
1 hour ago




In $D(0_n,sigma^2 I_n)$, if $0_n$ is the mean and $sigma^2$ = variance, which kind of distributions meet this condition, apart from normal?
– a_statistician
1 hour ago










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The OLS (Ordinary Least Squares) estimate does not depend on the distribution D, so for any distribution you can use the exact same tools as the for the normal distribution.



This just gives the OLS estimates of the parameters, it does not justify any tests or other inference that could depend on your distribution D (though the Central Limit Theorem holds for regression and for large enough sample sizes (how big depends on how non-normal D is) the normal based tests and inference will still be approximately correct.



If you want Maximum Likelihood estimation instead of OLS, then this will depend on D). The normal distribution has the advantage that OLS gives the Maximum Likelihood answer as well.






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    1 Answer
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    active

    oldest

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    1 Answer
    1






    active

    oldest

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    active

    oldest

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    active

    oldest

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    up vote
    3
    down vote













    The OLS (Ordinary Least Squares) estimate does not depend on the distribution D, so for any distribution you can use the exact same tools as the for the normal distribution.



    This just gives the OLS estimates of the parameters, it does not justify any tests or other inference that could depend on your distribution D (though the Central Limit Theorem holds for regression and for large enough sample sizes (how big depends on how non-normal D is) the normal based tests and inference will still be approximately correct.



    If you want Maximum Likelihood estimation instead of OLS, then this will depend on D). The normal distribution has the advantage that OLS gives the Maximum Likelihood answer as well.






    share|cite|improve this answer
























      up vote
      3
      down vote













      The OLS (Ordinary Least Squares) estimate does not depend on the distribution D, so for any distribution you can use the exact same tools as the for the normal distribution.



      This just gives the OLS estimates of the parameters, it does not justify any tests or other inference that could depend on your distribution D (though the Central Limit Theorem holds for regression and for large enough sample sizes (how big depends on how non-normal D is) the normal based tests and inference will still be approximately correct.



      If you want Maximum Likelihood estimation instead of OLS, then this will depend on D). The normal distribution has the advantage that OLS gives the Maximum Likelihood answer as well.






      share|cite|improve this answer






















        up vote
        3
        down vote










        up vote
        3
        down vote









        The OLS (Ordinary Least Squares) estimate does not depend on the distribution D, so for any distribution you can use the exact same tools as the for the normal distribution.



        This just gives the OLS estimates of the parameters, it does not justify any tests or other inference that could depend on your distribution D (though the Central Limit Theorem holds for regression and for large enough sample sizes (how big depends on how non-normal D is) the normal based tests and inference will still be approximately correct.



        If you want Maximum Likelihood estimation instead of OLS, then this will depend on D). The normal distribution has the advantage that OLS gives the Maximum Likelihood answer as well.






        share|cite|improve this answer












        The OLS (Ordinary Least Squares) estimate does not depend on the distribution D, so for any distribution you can use the exact same tools as the for the normal distribution.



        This just gives the OLS estimates of the parameters, it does not justify any tests or other inference that could depend on your distribution D (though the Central Limit Theorem holds for regression and for large enough sample sizes (how big depends on how non-normal D is) the normal based tests and inference will still be approximately correct.



        If you want Maximum Likelihood estimation instead of OLS, then this will depend on D). The normal distribution has the advantage that OLS gives the Maximum Likelihood answer as well.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 5 hours ago









        Greg Snow

        38.8k157121




        38.8k157121




















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