Mean squared error (MSE) of each gene by tissue-type. The sign is determined by the direction of the bias. The MSE is broken down into the contributing components of the squared bias (Bias2) and the variance (Sigma2). Dataset from Vandesompele et al. . Tissue types analyzed included normal bone marrow (BM), cultured normal fibroblasts (FIB), normal leukocytes (LEU), neuroblastoma cell lines (NB), and pooled normal tissue from breast, brain, fetal brain, heart, kidney, uterus, lung, trachea and small intestine (POOL).