er setup is for example <a href="http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE994">GSE994</a> where samples from current and former smokers were compared, using an Affymetrix microarray.</p>
<p>Data submitted to NCBI GEO can be both “raw” and “proceseed”. Let us focus on gene expression data for the moment. “Processed” data is normalized and quantified, typically at the gene level, and is usually provided in the form of a gene by sample matrix. “Raw” data can be anything, from sequen