When efficient model averaging out-performs boosting and bagging

The Bayes optimal classifier (BOC) is an ensemble technique used extensively in the statistics literature. However, compared to other ensemble techniques such as bagging and boosting, BOC is less known and rarely used in data mining. This is partly due to BOC being perceived as being inefficient and because bagging and boosting consistently outperforms a single model, which raises the question: "Do we even need BOC in datamining?". We show that the answer to this question is "yes" by illustrating several recent efficient model averaging approximations to BOC can significantly outperform bagging and boosting in realistic situations such as extensive class label noise, sample selection bias and many-class problems. That model averaging techniques outperform bagging and boosting in these situations has not been published in the machine learning, mining or statistical communities to our knowledge.