Gene expression fold changes (log 2 based) in the top 3 significant experimental sets inferred by GAGE or PAGE. For each gene set, the bar height represents mean and error bar represent standard error of gene expression fold changes induced by 8 hour BMP6 treatment in human MSC. GAGE uses two-sample t-test and PAGE does one-sample z-test. PAGE frequently selected gene sets with extreme up or down regulation in a few genes and almost no changes in the rest. Such gene sets have too large within-group variances to be called significantly different from the background based on two-sample t-test, even though their mean fold changes are big.