Thus, if binary classification on ERBB2 mRNA is desired, cutoff up-2 may represent a tradeoff between sensitivity (the fraction of HER2+ cancers that are correctly identified by ERBB2 mRNA assay as being HER2+) and specificity (the fraction of HER2− cancers that are correctly identified by ERBB2 mRNA assay as not being HER2+). Here, ERBB2 is linked to cancer.