Table 4.

Interpretation of Parity Plot Metrics

r	Minor slope	Interpretation	Case	Classification
≈1.0	≈1.0	Stable monotonic covariance of genes (both exhibit very similar expression trends)	Both exhibit stable, uniform expression	Good candidates
			Both exhibit same nonuniform trend	False positive
≈1.0	<1.0	Stable nonmonotonic covariance of genes (at least one exhibits nonuniform expression trend)	1 stable, 1 varies	False negative for stable gene
			Both vary	Bad candidates
<<1.0	Varies	At least 1 gene exhibits highly variable expression and/or nonlinear relationship between genes	1 stable, 1 nonlinear	False negative for stable gene
			Both vary nonlinearly	Bad candidates

The coefficient of correlation (R) and minor slope were extracted from the parity plots and subsequently utilized to rank reference gene stability. The interpretation of these metrics, cases that can lead to their values, and the classification in utilizing these metrics are detailed.