<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>Despite its enormous promise to further our understanding of cellular processes involved in the regulation of gene expression, microarray technology generates data
for which statistical pre-processing has become a necessity before any interpretation
of data can begin. The process by which we distinguish (and remove) non-biological
variation from biological variation is called <italic>normalization</italic>. With a multitude of
experimental designs, techniques and technologies influencing the acquisition of data,
numerous approaches to normalization have been proposed in the literature. The
purpose of this short review is not to add to the many suggestions that have been
made, but to discuss some of the difficulties we encounter when analysing microarray
data.</p>
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Comp Funct Genomics. 2002 Aug; 3(4):375-379