Effect of artifact size and preprocessing procedure on error of gene expression estimation. The size of the artifact describes the diameter of the circular artifact, with negative sizes indicating magnitude-reducing artifacts. The magnitude of applied artifacts was fixed at 2 fold (increase) or 0.5 fold (decrease) probe intensity in the footprint of the artifact. Error is calculated as the average absolute difference, in the log domain, between original gene expression and expression measured after application of artifacts. Error bars represent the standard deviation calculated across 3 trials.