These five samples are the same in the Training Set scanned in Instrument 1 and the Training Set scanned in Instrument 2, so it is clear that the problem is that the lab value does not correlate as the others with the spectra.First, we remove the samples from the Training Set 1:
Now, the new regression model without outliers, and with the math treatments we consider apropiate as MSC + Second derivative:
Comparing the summaries of the models with and without outliers we see the logical improvement.
Now with this table we can run the Monitor function:
The results show an improvement in the RMSEP and the SEP statistic tell us the error corrected by the bias. The monitor function now recommend a Bias adjustment.
The distribution of the residuals shows the bias problem, but it is quite uniform once we correct the bias.