Skip to main content
Figure 1 | BMC Bioinformatics

Figure 1

From: A Population Proportion approach for ranking differentially expressed genes

Figure 1

Summary of the Population Proportion Ranking Method. The inter-class variability is quantified by calculating the inter-class ratio of expression level of a sample in class T to its expression level in a sample in class N, for all possible combinations of samples in the two classes. Depending on the desired relative difference between the classes to identify a gene as differentially expressed, an inter-class ratio cutoff is chosen. The fraction of inter-class ratios calculated above, which are greater than this inter-class ratio cutoff, is calculated (fTN). Intra-class variability for a class is similarly quantified by calculating the intra-class ratios of expression level of a sample in the class to its expression level in every other sample in the same class. Analogous to the inter-class ratio cutoff, an intra-class ratio cutoff is chosen based on acceptable level of variability within a class. The fraction of intra-class ratios calculated above which are greater than the cutoff is calculated (fTT, fNN). Genes in which fTT and/or fNN fraction is significantly smaller than fTN are ranked based on an established statistical method of comparing population proportions.

Back to article page