1. A system for determining a background component of reporter ion signals, comprising: a mass spectrometer that analyzes a plurality of samples that include a protein labeled with a plurality of isobaric reporter ions at a plurality of different times, producing a plurality of mass spectra for the plurality of isobaric reporter ions; and a processor in communication with the mass spectrometer that obtains the plurality of mass spectra from the mass spectrometer, calculates a cumulative distribution for an inverse coefficient of differential expression of the plurality of mass spectra, fits a Pearson Type IV distribution shifted by a constant value to the cumulative distribution and solves for the constant value, and calculates a background component for each spectrum of the plurality of mass spectra from the constant value, a calculated coefficient of differential expression for the each spectrum, and an average reporter ion signal value for the each spectrum.