Abundance Ratio (PEAKS Q)

If we assume that the abundance ratio of any peptide belonging to a protein is representative of the abundance ratio of that protein, then in theory it follows that all peptides belonging to a protein should have the same abundance ratio.

An outlier is a data point within a data set where these values are statistically different from the main body of the data. Outliers have to be removed when calculating the protein abundance.

To find and remove outliers, PEAKS computes the ratio between the difference of the minimum [or maximum value] with its neighbor value and the difference of the maximum and minimum values. This ratio should follow a certain distribution. The outlying minimum [or maximum] value is removed from the data set if does not follow the underlying distribution. ^{[Xin et al.]}