A genoty ping batch consists of a set of samples that are processed together through the genotyping chemistry, hybridization and scanning stages. For the Affymetrix projects, a batch consisted of a 96-well plate and for the Illumina projects, a set of 24 samples (quarter-plate). Except for the Addiction project, samples were assigned to batches to balance case-control status and, in some projects, ethnicity. Each 96-well plate included one or more HapMap [International HapMap Consortium 2005] controls and some plates include study sample duplicates.
