Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Blinded and unblinded sample size re-estimation procedures for
  stepped-wedge cluster randomized trials   The ability to accurately estimate the sample size required by a
stepped-wedge (SW) cluster randomized trial (CRT) routinely depends upon the
specification of several nuisance parameters. If these parameters are
mis-specified, the trial could be over-powered, leading to increased cost, or
under-powered, enhancing the likelihood of a false negative. We address this
issue here for cross-sectional SW-CRTs, analyzed with a particular linear mixed
model, by proposing methods for blinded and unblinded sample size re-estimation
(SSRE). Blinded estimators for the variance parameters of a SW-CRT analyzed
using the Hussey and Hughes model are derived. Then, procedures for blinded and
unblinded SSRE after any time period in a SW-CRT are detailed. The performance
of these procedures is then examined and contrasted using two example trial
design scenarios. We find that if the two key variance parameters were
under-specified by 50%, the SSRE procedures were able to increase power over
the conventional SW-CRT design by up to 29%, resulting in an empirical power
above the desired level. Moreover, the performance of the re-estimation
procedures was relatively insensitive to the timing of the interim assessment.
Thus, the considered SSRE procedures can bring substantial gains in power when
the underlying variance parameters are mis-specified. Though there are
practical issues to consider, the procedure's performance means researchers
should consider incorporating SSRE in to future SW-CRTs.

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The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn