find.ncp {SharedHT2} | R Documentation |
In order to provide a yardstick in designing simulation experiments this function calculates the non-centrality parameter for a simple F test of the null hypothesis of zero group means
find.ncp(e.I, e.II, nreps, d)
e.I |
type I error i.e. level of significance |
e.II |
type II error i.e. 1-power |
nreps |
# replicates |
d |
# groups |
An numeric vector of length 2 containing the calculated non-centrality parameter and the corresponding power of the standard F test of the null hypothesis that all group means are zero.
theta |
The non-centrality parameter |
power |
Corresponding power |
Once you derive the non-centrality parameter then you can use it
in specifying the population means for genes having differential expression.
For example if investiagation using find.ncp
turns up the value
7.5 then use $7.5/nreps^{0.5}$ to specify group means corresponding to
experimental conditions under which the gene is differentially expressed.
Grant Izmirlian izmirlian@nih.gov
EBfit
, SimAffyDat
TopGenes
,
SimW.IW
, Simnu.mix
find.ncp(0.005, 0.0316, 3, 2)