Comparison of different microarray data sets at gene set level shows better congruence than comparison at gene level. A. Comparison of two different microarray data sets at gene level. Two microarray data sets, GDS 287 (Muscle function and aging-Male) and GDS 472 (Muscle function and aging-Female) were analyzed, significantly changed genes (|fold change| > 1.5 and t-test p < 0.05) from each data set were selected, and the percentage of common gene lists for both data sets was calculated. B. Comparison at gene set level. We first performed PAGE on the two microarray data sets, selected significant gene sets (p < 0.05), and calculated percentage of common gene sets for both data sets.