The density distributions of the probes in AP4 divide into high and low components. The expression values are for the four probes from the ER+ samples in the TRANSBIG cohort. The density distribution of each probe shows a large component with low baseline expression and small standard deviation, and a long right tail with elevated expression. The mixture model method applied here calculates cutoffs between the two components, indicated by the dotted vertical lines. In each case, the high component is significantly enriched with metastatic cases. The ratios of the low components are: CDC6, 0.95; MKI67 (212022_s_at), 0.85; MKI67 (212020_s_at), 0.89; SPAG5, 0.85. The ratio cutoff for being considered a multi-state probe in this cohort is 0.83.