Statistics and Data Analysis for Microarrays Using R and Bioconductor, 2nd Edition

Classical approaches to data analysis 389

where the number of degree s of freedom is ν = n

1

+ n

2

− 2 and the standard

error s

X

1

−X

2

is:

s

X

1

−X

2

=

s

s

2

p



1

n

1

+

1

n

2



12.4 Summary

This chapter discussed a number of statistical techniques that can be used

directly to answer questions that arise in the a nalysis o f microarray data. The

chapter addressed only par ametric testing involving one or two s amples. A

sample in this context is a set of measurements. Such measur e ments can be:

Repe ated measurements of the expression level of a gene in various in-

dividuals of a biological population (biological replicates)

Repe ated measurements of the expression level of