[Arrays] standard error of fold change when using a Universal
(by amcarthur from mac.com)
Mon Jun 18 09:05:30 EST 2007
We have performed an experiment that included replicated microarray
analyses. We have 4 replicate RNA samples from three treatments (A,
B, C) plus a Universal Reference RNA sample (UR) made up of equal
amounts of all A, B, and C samples.
All experimental RNA samples (A1, A2, A3, A4, B1, B2, B3, B4, C1, C2,
C3, C4) were Cy3 labeled and individually co-hybridized with Cy5
labeled Universal Reference. When all was said and done we
calculated the mean and standard error for fold change of A, B, and C
versus the Universal Reference.
Now we want to calculate "through" the Universal Reference to compare
A versus B. To calculate the mean fold change of A versus B we have
simply divided the mean fold change of A against the UR by the mean
fold change of B against the UR. The question now is how to
calculate the standard error of the fold change of A versus B.
Does anyone have a good reference for calculating the standard error
of a ratio variable when the ratio is made of two means with their
own standard errors?
Andrew G. McArthur, Ph.D.
Email: amcarthur from mac.com, Web: http://mcarthurlab.blogspot.com
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