DNA Microarray Example

DNA Microarray Example

Sample Size for t-test for fold change

For the first time, planners of DNA Microarray studies can easily figure out what sample size will be needed to detect specific fold-changes using a specified p-value. You can even compute expected detection rate when a fold-change threshold is specified. nQuery Advisor’s® easy-to-use tables and plots can assist in interpretation of results for multiple genes.

For example, in a gene expression study, results for each gene were compared between two groups (with 3 microarrays each) using a two-sided 1% t-test. Of the genes with significant differences, only those genes for which the observed fold-change is greater than or equal to 2 will be studied further.

The researcher can conclude that for studies of this size, the selection rule used would have found essentially all the genes whose true fold-change exceeds 6, 90% or more of the genes with a true fold-change of 4 or more, but only 25% of genes with a true fold-change of 2 will be studied further.