The FDR (Benjamini Hochberg) method (Benjamini Hochberg, 1995) is the default P-value adjustment method in ArrayStar. In this method, the P-values are first sorted and ranked. The smallest value gets rank 1, the second rank 2, and the largest gets rank N. Then, each P-value is multiplied by N and divided by its assigned rank to give the adjusted P-values.
In order to restrict the false discovery rate to (say) 0.05, all the genes with adjusted P-values less than 0.05 are selected. This method aims to reduce what is called the False Discovery Rate (FDR) and is used when the objective is to reduce the number of false positives and to increase the chances of identifying all the differentially expressed genes.