I have 12 U74Av2 microarrays (and their B and C counterparts). I used SimpleAffy to make an AffyBatch of the raw data from the CEL files, and normalized with MAS5. On plotting QC, I discovered that 3 of the arrays were outliers (see plot attached). Looking at AffyRNADeg, the 3 arrays have a different slope than the rest of the arrays (plot attached). Questions are: 1. Does the degradation difference explain the normalization problem? 2. Is there a way to compensate for this? 3. Could one normalize those separately and then somehow cross normalize the two groups of arrays (in terms of degradation properties)? I also normalized with GCRMA, but the QC tools don't work the same way (as they won't given the nature of the tools and the normalization algorithms), but they still don't look like the rest of the group (box plot attached). Thanks, Anand C. Patel, MD Washington University School of Medicine acpatel@usa.net -------------- next part -------------- A non-text attachment was scrubbed... Name: qc_plot.png Type: image/png Size: 33030 bytes Desc: not available Url : https://stat.ethz.ch/pipermail/bioconductor/attachments/20050328 /bd165742/qc_plot.png -------------- next part -------------- A non-text attachment was scrubbed... Name: rna_deg.png Type: image/png Size: 23680 bytes Desc: not available Url : https://stat.ethz.ch/pipermail/bioconductor/attachments/20050328 /bd165742/rna_deg.png -------------- next part -------------- A non-text attachment was scrubbed... Name: gcrma_boxplot.png Type: image/png Size: 15334 bytes Desc: not available Url : https://stat.ethz.ch/pipermail/bioconductor/attachments/20050328 /bd165742/gcrma_boxplot.png