I am trying to get information about the output produced by the bounds
function. Code that runs the package along with sample output is below.
Questions (1) Do the values given under boundaries, lower and upper
(Boundaries:
Time Lower Upper Exit pr. Diff. pr.
1 0.10 -6.9913 6.9913 2.7227e-12 2.7227e-12
2 0.33 -3.7308 3.7308 1.9097e-04 1.9097e-04
3 1.00 -1.9605 1.9605 5.0000e-02 4.9809e-02)
represent values of z-scores which an analysis must exceed to declare the
analysis significant (after accounting for multiple looks)?
(2) The Exit pr. is described in the documentation as
exit.pr
the vector of cumulative exit probabilities at each analysis.
What is meant by "exit probabilites"
(3) Diff. pr. is described in the documentation as
diff.pr
the vector of exit probabilities accumulated at each analysis.
What is meant by "exit probabilities accumulated"?
Thank you,
John
install.packages("ldbounds")
library(ldbounds)
t2 <- c(0.10,0.33,1)
t2
obf.bd <- bounds(t2,iuse=c(1,1),alpha=c(0.025,0.025))
summary(obf.bd)
plot(obf.bd)
Lan-DeMets bounds for a given spending function
n = 3
Overall alpha: 0.05
Type: Two-Sided Symmetric Bounds
Lower alpha: 0.025
Upper alpha: 0.025
Spending function: O'Brien-Fleming
Boundaries:
Time Lower Upper Exit pr. Diff. pr.
1 0.10 -6.9913 6.9913 2.7227e-12 2.7227e-12
2 0.33 -3.7308 3.7308 1.9097e-04 1.9097e-04
3 1.00 -1.9605 1.9605 5.0000e-02 4.9809e-02
John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric
Medicine
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
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