Metrohm Vision – Theory - Manual (Page 25)

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5.4.2 Analysis of an Unknown
Using a products’ principal component model, the residual variance of the unknown spectrum is
calculated using primary eigenvectors. The variance is scaled or the probability calculated (depending
on the choice of threshold). The unknown passes analysis if the calculated residual is below the
threshold value.
Note: If the probability threshold type is used, Vision calculates the probability that a sample is not a
member of the distribution described by the training set. A low value for this quantity indicates a high
probability that the sample spectrum belongs to the training set.