Fig. 2

Spectral features. a Mean absorbance difference per wavenumber between cases and references (differential fingerprint) b Effect size per wavenumber. This quantity is known as the Cohen’s d in signal detection theory and corresponds to the standardized difference between the mean absorbance of the cases and references. The dashed line indicates effect size of one standard deviation. c P-values per wavenumber, by performing local two-sided t-tests. d ROC AUC extracted by the Mann-Whitney U-test. The dashed line corresponds to the AUC value of the trained SVM model. The shaded rectangular areas, in all panels, indicate spectral regions where highly-significant differences have been identified