Specifically, we observe t-test p-values ranging from 0.34 -0.90 with the notable exception of NIST/RMSE with a p-value of 9.3 x 10 -9 . In other words, the predicted spectra for underivatized amino acids within the NIST library produced a significantly broader range prediction accuracy when measured by RMSE than all other distributions considered. It completely eludes us why free amino acids in this sample, measured in this way, should be so different from free amino acids in other samples given that the IOCB library covers much the same physicochemical range as the NIST library.