Comparison Between Product and Mean Classi er Combination Rules

To obtain better classi cation results the outputs of an ensemble of classi ers can be combined instead of just choosing the best classi er This combining is often done by using a simple linear combination of the outputs of the classi ers or by using order statistics using the order in the outputs for di erent classes In this paper we will show that using the normalized product of the outputs of the classi ers can be more powerful for classi cation performance We will show in which cases a product combination is to be preferred and where a combination by averaging can be more useful This will be supported by theoretical and experimental observations