Spearman correlation coefficients of line intensity (left panel) and average dense gas to CO line ratios (right panel) as a function of physical galactic properties (Sect. 2.3). An increased S/N will directly result in a lower correlation coefficient. We therefore expect higher correlation coefficients for HCN, followed by HCO⁺, then HNC, then N₂H⁺ as a function of the same galactic properties. All p values are below 5% except p values for the line/CO ratios as a function of σ_CO.