Sorry for messed up text. Here it goes again:
I am learning to use the gsDesign package.
I have a question about Pocock and OBF boundary. As far as I can understand,
these 2 boundaries require equal spacing between interim analyses (maybe this
is not correct?). But looks like I can still use gsDesign to run an analysis
based on unequal spacing:
> gsDesign(k=2,test.type=2,timing=c(0.75,1),alpha=0.05,sfu='Pocock')
Symmetric two-sided group sequential design with 90 %power and 5 % Type I
Error.Spending computations assume trial stops if a bound is crossed.
Sample Size Analysis Ratio* Z Nominal p Spend 1 0.796 1.82
0.0346 0.0346 2 1.061 1.82 0.0346 0.0154 Total
0.0500 ++alpha spending: Pocock boundary.*Sample size ratio compared to
fixed design with no interim
Can anyone share some light whether the above analysis is still valid? Or for
unequal spacing, I have to use Lan-Demet’s error spending function
approximations? Thank you,
From: Berend Hasselman <b...@xs4all.nl>
To: array chip <arrayprof...@yahoo.com>
Cc: R-help Mailing List <r-help@r-project.org>
Sent: Friday, September 22, 2017 11:46 PM
Subject: Re: [R] gsDesign Pocock & OBF boundary
> On 23 Sep 2017, at 01:32, array chip via R-help <r-help@r-project.org> wrote:
>
> Hi,
>
> I am learning to use your gsDesign package! I have a question about Pocock
> and OBF boundary. As far as Iunderstand, these 2 boundaries require equal
> spacing between interim analyses(maybe this is not correct?). But I can still
> use gsDesign to run an analysisbased on unequal spacing:
> gsDesign(k=2,test.type=2,timing=c(0.75,1),alpha=0.05,sfu='Pocock')Symmetrictwo-sided
> group sequential design with90 %power and 5 % Type I
> Error.Spendingcomputations assume trial stops if a bound is crossed.
> Sample Size AnalysisRatio* Z Nominal p Spend 1 0.796
> 1.82 0.0346 0.0346 2 1.061 1.82 0.0346 0.0154 Total
> 0.0500 ++alpha spending:Pocockboundary.*Sample size ratio
> compared to fixed design with no interim Can anyone share some light whether
> the above analysis is stillvalid? Or for unequal spacing, I have to use
> Lan-Demet’s error spendingfunction approximations? Thank you,
> [[alternative HTML version deleted]]
>
Your example code is a complete mess.
Do NOT post in html. This is a plain text mailing list.
Read the Posting Guide (https://www.r-project.org/posting-guide.html).
Berend Hasselman]
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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[[alternative HTML version deleted]]
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