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Activity Number: 102
Type: Contributed
Date/Time: Monday, July 30, 2007 : 8:30 AM to 10:20 AM
Sponsor: Biometrics Section
Abstract - #310045
Title: Improved Significance of Microarrays
Author(s): Shunpu Zhang*+
Companies: University of Nebraska-Lincoln
Address: Department of Statistics, Lincoln, NE, 68583-0963,
Keywords: microarray ; null statistics ; test statistics ; false discovery rate ; false positive ; fudge factor
Abstract:

The Significance Analysis of Microarrays (SAM) is a popular method for detecting significantly expressed genes and controlling the false discovery rate (FDR). However, it has been recently reported in the literature that SAM tends to over-estimate the FDR. In this paper, we propose an improved significance analysis of microarrays (ISAM) method. The improvement is achieved by employing the more efficient test and null statistics of Zhang (2006) and a novel way of choosing the fudge factor. Through extensive simulations, we show that our proposed method consistently outperforms SAM in the sense that it tends to contain smaller number of true false positive (FP) given that the same number of significant genes is identified by SAM and our proposed method. We also demonstrate that our proposed method provides reasonably unbiased estimates of the FDR.


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Revised September, 2007