Comparing three methods for variance estimation with duplicated high density oligonucleotide arrays |
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Authors: | Huang Xiaohong Pan Wei |
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Institution: | (1) Division of Biostatistics, School of Public Health, University of Minnesota, A460 Mayo Building (MMC 303), Minneapolis, MN 55455–0378, USA, |
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Abstract: | Microarray experiments are being increasingly used in molecular biology. A common task is to detect genes with differential
expression across two experimental conditions, such as two different tissues or the same tissue at two time points of biological
development. To take proper account of statistical variability, some statistical approaches based on the t-statistic have been proposed. In constructing the t-statistic, one needs to estimate the variance of gene expression levels. With a small number of replicated array experiments,
the variance estimation can be challenging. For instance, although the sample variance is unbiased, it may have large variability,
leading to a large mean squared error. For duplicated array experiments, a new approach based on simple averaging has recently
been proposed in the literature. Here we consider two more general approaches based on nonparametric smoothing. Our goal is
to assess the performance of each method empirically. The three methods are applied to a colon cancer data set containing
2,000 genes. Using two arrays, we compare the variance estimates obtained from the three methods. We also consider their impact
on the t-statistics. Our results indicate that the three methods give variance estimates close to each other. Due to its simplicity
and generality, we recommend the use of the smoothed sample variance for data with a small number of replicates.
Electronic Publication |
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Keywords: | Differential gene expression Microarray Nonparametric smoothing |
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