Concepts of the PriOmics peptide aggregation strategies. Both methods account for the protein affiliation, but prior CIG (conditionally independent variables–grouped) (A) removes edges a priori between proteotypic peptides of a protein, whereas prior non-CIG (nonconditionally independent variables–grouped) (B) retains them. The former is more appropriate for technical, noisy copies of an identical variable (peptides that represent the same protein abundance), and the latter is more appropriate for variables that are related but likely represent different biological variables (e.g., different phosphorylation sites of the same protein).