[R] output of bounds function (ldbounds package)

Sorkin, John j@ork|n @end|ng |rom @om@um@ry|@nd@edu
Fri Mar 13 10:24:48 CET 2020

```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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