# Questions tagged [classification]

Statistical classification is the problem of identifying the sub-population to which new observations belong, where the identity of the sub-population is unknown, on the basis of a training set of data containing observations whose sub-population is known. Therefore these classifications will show a variable behavior which can be studied by statistics.

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### Reduce Classification Probability Threshold

I have a question regarding classification in general. Let $f$ be a classifier, which outputs a set of probabilities given some data D. Normally, one would say: well, if $P(c|D) > 0.5$, we will ...
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### When is unbalanced data really a problem in Machine Learning?

We already had multiple questions about unbalanced data when using logistic regression, SVM, decision trees, bagging and a number of other similar questions, what makes it a very popular topic! ...
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### Compare classifiers based on AUROC or accuracy?

I have a binary classification problem and I experiment different classifiers on it: I want to compare the classifiers. which one is a better measure AUC or accuracy? And why? ...
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### How do you know that your classifier is suffering from class imbalance?

In cases where there is a substantial difference in relative class frequencies, it could be that the density of the minority class is never higher than the density of the majority class anywhere in ...
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### Opinions about Oversampling in general, and the SMOTE algorithm in particular [closed]

What is your opinion about oversampling in classification in general, and the SMOTE algorithm in particular? Why would we not just apply a cost/penalty to adjust for imbalance in class data and any ...
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### What is "baseline" in precision recall curve

I'm trying to understand precision recall curve, I understand what precision and recall are but the thing I don't understand is the "baseline" value. I was reading this link https://classeval....
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### What measure of training error to report for Random Forests?

I'm currently fitting random forests for a classification problem using the randomForest package in R, and am unsure about how to report training error for these ...
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