Why Naive Bayes classifier is known to be a bad estimator?





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In scikit-learn documentation page for Naive Bayes, it states that: On the flip side, although naive Bayes is known as a decent classifier, it is known to be a bad estimator, so the probability outputs from predict_proba are not to be taken too seriously.



I want to use Naive Bayes for a classification problem of two categorical dataset, and I'm interested to know why the output of predict_proba could not be taken as a accurate prediction? The reason why I'm asking this question is that, my ultimate purpose after training this dataset is to use this trained model to predict the probabilities on a test dataset and if it does not have a good accuracy, so it seems it would not be a good fit for my case. I appreciate if someone could explain it.










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    $begingroup$


    In scikit-learn documentation page for Naive Bayes, it states that: On the flip side, although naive Bayes is known as a decent classifier, it is known to be a bad estimator, so the probability outputs from predict_proba are not to be taken too seriously.



    I want to use Naive Bayes for a classification problem of two categorical dataset, and I'm interested to know why the output of predict_proba could not be taken as a accurate prediction? The reason why I'm asking this question is that, my ultimate purpose after training this dataset is to use this trained model to predict the probabilities on a test dataset and if it does not have a good accuracy, so it seems it would not be a good fit for my case. I appreciate if someone could explain it.










    share|cite|improve this question









    $endgroup$















      2












      2








      2





      $begingroup$


      In scikit-learn documentation page for Naive Bayes, it states that: On the flip side, although naive Bayes is known as a decent classifier, it is known to be a bad estimator, so the probability outputs from predict_proba are not to be taken too seriously.



      I want to use Naive Bayes for a classification problem of two categorical dataset, and I'm interested to know why the output of predict_proba could not be taken as a accurate prediction? The reason why I'm asking this question is that, my ultimate purpose after training this dataset is to use this trained model to predict the probabilities on a test dataset and if it does not have a good accuracy, so it seems it would not be a good fit for my case. I appreciate if someone could explain it.










      share|cite|improve this question









      $endgroup$




      In scikit-learn documentation page for Naive Bayes, it states that: On the flip side, although naive Bayes is known as a decent classifier, it is known to be a bad estimator, so the probability outputs from predict_proba are not to be taken too seriously.



      I want to use Naive Bayes for a classification problem of two categorical dataset, and I'm interested to know why the output of predict_proba could not be taken as a accurate prediction? The reason why I'm asking this question is that, my ultimate purpose after training this dataset is to use this trained model to predict the probabilities on a test dataset and if it does not have a good accuracy, so it seems it would not be a good fit for my case. I appreciate if someone could explain it.







      machine-learning classification naive-bayes






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      asked Mar 27 at 15:48









      Alone ProgrammerAlone Programmer

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          $begingroup$

          Because it's Naive (see wikipedia): it assumes the features are independent, the probabilities are incorrect if this assumption is not correct.
          eg assume you are predicting mortality based on smoking and drinking. NB may well identify people who smoke and drink as higher risk (=probability), just because there is a correlation between smoking and drinking.
          Suggest you setup a contingency table for eg smoking, drinking, dying and calcuate Naive bayes. probabilities vs true probabilities



          why don't you use logistic regression instead?






          share|cite|improve this answer









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          • $begingroup$
            The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
            $endgroup$
            – Alone Programmer
            Mar 27 at 16:14












          Your Answer





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          1 Answer
          1






          active

          oldest

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          1 Answer
          1






          active

          oldest

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          active

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          active

          oldest

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          3












          $begingroup$

          Because it's Naive (see wikipedia): it assumes the features are independent, the probabilities are incorrect if this assumption is not correct.
          eg assume you are predicting mortality based on smoking and drinking. NB may well identify people who smoke and drink as higher risk (=probability), just because there is a correlation between smoking and drinking.
          Suggest you setup a contingency table for eg smoking, drinking, dying and calcuate Naive bayes. probabilities vs true probabilities



          why don't you use logistic regression instead?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
            $endgroup$
            – Alone Programmer
            Mar 27 at 16:14
















          3












          $begingroup$

          Because it's Naive (see wikipedia): it assumes the features are independent, the probabilities are incorrect if this assumption is not correct.
          eg assume you are predicting mortality based on smoking and drinking. NB may well identify people who smoke and drink as higher risk (=probability), just because there is a correlation between smoking and drinking.
          Suggest you setup a contingency table for eg smoking, drinking, dying and calcuate Naive bayes. probabilities vs true probabilities



          why don't you use logistic regression instead?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
            $endgroup$
            – Alone Programmer
            Mar 27 at 16:14














          3












          3








          3





          $begingroup$

          Because it's Naive (see wikipedia): it assumes the features are independent, the probabilities are incorrect if this assumption is not correct.
          eg assume you are predicting mortality based on smoking and drinking. NB may well identify people who smoke and drink as higher risk (=probability), just because there is a correlation between smoking and drinking.
          Suggest you setup a contingency table for eg smoking, drinking, dying and calcuate Naive bayes. probabilities vs true probabilities



          why don't you use logistic regression instead?






          share|cite|improve this answer









          $endgroup$



          Because it's Naive (see wikipedia): it assumes the features are independent, the probabilities are incorrect if this assumption is not correct.
          eg assume you are predicting mortality based on smoking and drinking. NB may well identify people who smoke and drink as higher risk (=probability), just because there is a correlation between smoking and drinking.
          Suggest you setup a contingency table for eg smoking, drinking, dying and calcuate Naive bayes. probabilities vs true probabilities



          why don't you use logistic regression instead?







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Mar 27 at 16:09









          seanv507seanv507

          3,1271019




          3,1271019












          • $begingroup$
            The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
            $endgroup$
            – Alone Programmer
            Mar 27 at 16:14


















          • $begingroup$
            The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
            $endgroup$
            – Alone Programmer
            Mar 27 at 16:14
















          $begingroup$
          The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
          $endgroup$
          – Alone Programmer
          Mar 27 at 16:14




          $begingroup$
          The reason why I wanted to use Naive Bayes first is that: in fact it does not have any hyper parameter to tune and could be a good starting point for me as non data scientist and an engineer.
          $endgroup$
          – Alone Programmer
          Mar 27 at 16:14


















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