. An illustration of the t test applied to two genes of the letrozole drug data.

e 6.3(a) shows the distribution of the t statistic values of the t test

as applied to the letrozole drug data. It shows a typical bell-shaped

tion. Figure 6.3(b) shows the distribution of the t test p values for

It shows a mixture of a decay Gamma distribution of DEGs and

m distribution of non-DEGs, which is a typical p value distribution

et al., 2001; Storey and Tibshirani, 2003].

pplying the t test to the letrozole drug data. (a) The t statistic distribution.

alue distribution.

e Type I and Type II errors

e stands for a tolerated error when making a decision. For any

made, there might be two types of errors. They are the Type I

the Type II error. They are important subjects in all statistical

nce analysis based on the use of p values [Markel, 1991; Yarandi,

au, et al., 2010]. For a commonly used critical p value 0.05, the

is 5% among the denied null hypotheses. This means that at least

00 null hypotheses, which have been rejected, may be true