Why no variance term in Bayesian logistic regression?












2












$begingroup$


I've read here that




... (Bayesian linear regression) is most similar to Bayesian inference
in logistic regression, but in some ways logistic regression is even
simpler, because there is no variance term to estimate, only the
regression parameters.




Why is it the case, why no variance term in Bayesian logistic regression?










share|cite|improve this question









$endgroup$

















    2












    $begingroup$


    I've read here that




    ... (Bayesian linear regression) is most similar to Bayesian inference
    in logistic regression, but in some ways logistic regression is even
    simpler, because there is no variance term to estimate, only the
    regression parameters.




    Why is it the case, why no variance term in Bayesian logistic regression?










    share|cite|improve this question









    $endgroup$















      2












      2








      2


      1



      $begingroup$


      I've read here that




      ... (Bayesian linear regression) is most similar to Bayesian inference
      in logistic regression, but in some ways logistic regression is even
      simpler, because there is no variance term to estimate, only the
      regression parameters.




      Why is it the case, why no variance term in Bayesian logistic regression?










      share|cite|improve this question









      $endgroup$




      I've read here that




      ... (Bayesian linear regression) is most similar to Bayesian inference
      in logistic regression, but in some ways logistic regression is even
      simpler, because there is no variance term to estimate, only the
      regression parameters.




      Why is it the case, why no variance term in Bayesian logistic regression?







      logistic bayesian variance






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked 2 hours ago









      PatrickPatrick

      1396




      1396






















          1 Answer
          1






          active

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          7












          $begingroup$

          Logistic regression, Bayesian or not, is a model defined in terms of Bernoulli distribution. The distribution is parametrized by "probability of success" $p$ with mean $p$ and variance $p(1-p)$, i.e. the variance directly follows from the mean. So there is no "separate" variance term, this is what the quote seems to say.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
            $endgroup$
            – seanv507
            2 hours ago










          • $begingroup$
            @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
            $endgroup$
            – Patrick
            1 hour ago








          • 1




            $begingroup$
            @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
            $endgroup$
            – Tim
            1 hour ago










          • $begingroup$
            @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
            $endgroup$
            – Firebug
            57 mins ago












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          1 Answer
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          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          7












          $begingroup$

          Logistic regression, Bayesian or not, is a model defined in terms of Bernoulli distribution. The distribution is parametrized by "probability of success" $p$ with mean $p$ and variance $p(1-p)$, i.e. the variance directly follows from the mean. So there is no "separate" variance term, this is what the quote seems to say.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
            $endgroup$
            – seanv507
            2 hours ago










          • $begingroup$
            @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
            $endgroup$
            – Patrick
            1 hour ago








          • 1




            $begingroup$
            @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
            $endgroup$
            – Tim
            1 hour ago










          • $begingroup$
            @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
            $endgroup$
            – Firebug
            57 mins ago
















          7












          $begingroup$

          Logistic regression, Bayesian or not, is a model defined in terms of Bernoulli distribution. The distribution is parametrized by "probability of success" $p$ with mean $p$ and variance $p(1-p)$, i.e. the variance directly follows from the mean. So there is no "separate" variance term, this is what the quote seems to say.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
            $endgroup$
            – seanv507
            2 hours ago










          • $begingroup$
            @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
            $endgroup$
            – Patrick
            1 hour ago








          • 1




            $begingroup$
            @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
            $endgroup$
            – Tim
            1 hour ago










          • $begingroup$
            @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
            $endgroup$
            – Firebug
            57 mins ago














          7












          7








          7





          $begingroup$

          Logistic regression, Bayesian or not, is a model defined in terms of Bernoulli distribution. The distribution is parametrized by "probability of success" $p$ with mean $p$ and variance $p(1-p)$, i.e. the variance directly follows from the mean. So there is no "separate" variance term, this is what the quote seems to say.






          share|cite|improve this answer









          $endgroup$



          Logistic regression, Bayesian or not, is a model defined in terms of Bernoulli distribution. The distribution is parametrized by "probability of success" $p$ with mean $p$ and variance $p(1-p)$, i.e. the variance directly follows from the mean. So there is no "separate" variance term, this is what the quote seems to say.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 2 hours ago









          TimTim

          59.7k9131224




          59.7k9131224












          • $begingroup$
            @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
            $endgroup$
            – seanv507
            2 hours ago










          • $begingroup$
            @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
            $endgroup$
            – Patrick
            1 hour ago








          • 1




            $begingroup$
            @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
            $endgroup$
            – Tim
            1 hour ago










          • $begingroup$
            @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
            $endgroup$
            – Firebug
            57 mins ago


















          • $begingroup$
            @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
            $endgroup$
            – seanv507
            2 hours ago










          • $begingroup$
            @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
            $endgroup$
            – Patrick
            1 hour ago








          • 1




            $begingroup$
            @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
            $endgroup$
            – Tim
            1 hour ago










          • $begingroup$
            @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
            $endgroup$
            – Firebug
            57 mins ago
















          $begingroup$
          @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
          $endgroup$
          – seanv507
          2 hours ago




          $begingroup$
          @patrick for linear regression $y = mx + c + epsilon$, whereas logistic regression p(y=1|x) = logistic(mx +c).
          $endgroup$
          – seanv507
          2 hours ago












          $begingroup$
          @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
          $endgroup$
          – Patrick
          1 hour ago






          $begingroup$
          @seanv507 and would it make sense to have $p(y=1|x)=logistic(mx+c+epsilon)$ or not? If not, is it because $p()$ is a probability and already includes some uncertainty?
          $endgroup$
          – Patrick
          1 hour ago






          1




          1




          $begingroup$
          @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
          $endgroup$
          – Tim
          1 hour ago




          $begingroup$
          @Patrick what would this formulation exactly mean? Could you give an example where would you imagine it to be used?
          $endgroup$
          – Tim
          1 hour ago












          $begingroup$
          @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
          $endgroup$
          – Firebug
          57 mins ago




          $begingroup$
          @Patrick When you describe the conditional expectation in terms of a distribution there's no error term.
          $endgroup$
          – Firebug
          57 mins ago


















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