Biomedical Engineering Reference
In-Depth Information
Intra-microarray comparisons, in which spotting is duplicated within the same microarray, allow the
statistical analysis to control for variability in the spotting process at the expense of fewer gene
expression experiments per microarray. If three spots are used per expression experiment, then one
of the three spots that are contaminated can be identified through statistical analysis of the relative
intensities (see Figure 6-17 ).
Figure 6-17. Intra-Microarray Intensity Comparisons. Statistical analysis of
the means of relative fluorescence intensity can be used to
programmatically identify a contaminated sample (far right) that can be
discarded from the final gene expression analysis, thereby reducing
variability in the experiment.
Although the mean intensity of fluorescence from Sample 3 in Figure 6-17 is, by visual inspection,
obviously different from the means of Samples 1 and 2, the issue is whether this difference is
statistically significant—that is, if the difference can't be explained by chance alone. Whether or not
the differences in mean values (depicted in a frequency plot in Figure 6-18 ) are significant depends
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