E LIFE SC

enable the screening of a biological sample for expressions of thousands of genes simultaneously under a variety of conditions [2], [3]. These genes contain information for making proteins that are essential to the structure and function of living cells. A major task in microarray studies is to select genes associated with specific physiological or pathological conditions. Given a set of candi-date genes, there are two possible gene selection targets, namely differentially expressed genes and relevant genes. A gene is “differentially expressed ” when it exhibits a certain distribution of expression levels under one condition and a sig-nificantly different distribution of expression levels under another condition. A gene is “relevant ” in terms of a Bayes decision rule if removal of the gene alone will result in perfor-mance deterioration of an optimal Bayes rule used for classify