title: A simple method for statistical analysis of intensity differences in microarray-derived gene expression data.
abstract: BACKGROUND
  Microarray experiments offer a potent solution to the problem of making and comparing large numbers of gene expression measurements either in different cell types or in the same cell type under different conditions. Inferences about the biological relevance of observed changes in expression depend on the statistical significance of the changes. In lieu of many replicates with which to determine accurate intensity means and variances, reliable estimates of statistical significance remain problematic. Without such estimates, overly conservative choices for significance must be enforced.
  
  
  RESULTS
  A simple statistical method for estimating variances from microarray control data which does not require multiple replicates is presented. Comparison of datasets from two commercial entities using this difference-averaging method demonstrates that the standard deviation of the signal scales at a level intermediate between the signal intensity and its square root. Application of the method to a dataset related to the beta-catenin pathway yields a larger number of biologically reasonable genes whose expression is altered than the ratio method.
  
  
  CONCLUSIONS
  The difference-averaging method enables determination of variances as a function of signal intensities by averaging over the entire dataset. The method also provides a platform-independent view of important statistical properties of microarray data.
authors.affiliation: Arcaris, Inc (Currently Deltagen Proteomics, Inc) Salt Lake City, UT, USA. kamb@arcaris.com
authors.forename: A
authors.initials: A
authors.lastname: Kamb
authors.forename: M
authors.initials: M
authors.lastname: Ramaswami
mesh_terms: D000465:Algorithms; D000818:Animals; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics; D020869:Gene Expression Profiling / Q000379:methods*; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D015203:Reproducibility of Results; D013223:Statistics as Topic; D015534:Trans-Activators / Q000378:metabolism; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D051176:beta Catenin