14,558 research outputs found
Computer program determines inventory size
FORTRAN 4 computer program calculates optimum size of a small inventory of relatively complex or expensive items. This program can be used in situations where the initial cost of purchase is large or when there is a need for a balanced inventory on a short production run
Monte Carlo Calculation of Energy Strain on a Muscle Fiber Due to Light Absorption
Monte Carlo models of light propagation in different materials are widely used in today’s science. In this paper the model is applied to a optically non-linear theoretical sample of a muscle fiber to determine the behavior of a photon inside the tissue, the energy absorbed by the sample and matching the energy strain to a possible effect on the fiber
Treatment Effect Quantification for Time-to-event Endpoints -- Estimands, Analysis Strategies, and beyond
A draft addendum to ICH E9 has been released for public consultation in
August 2017. The addendum focuses on two topics particularly relevant for
randomized confirmatory clinical trials: estimands and sensitivity analyses.
The need to amend ICH E9 grew out of the realization of a lack of alignment
between the objectives of a clinical trial stated in the protocol and the
accompanying quantification of the "treatment effect" reported in a regulatory
submission. We embed time-to-event endpoints in the estimand framework, and
discuss how the four estimand attributes described in the addendum apply to
time-to-event endpoints. We point out that if the proportional hazards
assumption is not met, the estimand targeted by the most prevalent methods used
to analyze time-to-event endpoints, logrank test and Cox regression, depends on
the censoring distribution. We discuss for a large randomized clinical trial
how the analyses for the primary and secondary endpoints as well as the
sensitivity analyses actually performed in the trial can be seen in the context
of the addendum. To the best of our knowledge, this is the first attempt to do
so for a trial with a time-to-event endpoint. Questions that remain open with
the addendum for time-to-event endpoints and beyond are formulated, and
recommendations for planning of future trials are given. We hope that this will
provide a contribution to developing a common framework based on the final
version of the addendum that can be applied to design, protocols, statistical
analysis plans, and clinical study reports in the future.Comment: 37 page
Maximum likelihood estimation of a log-concave density and its distribution function: Basic properties and uniform consistency
We study nonparametric maximum likelihood estimation of a log-concave
probability density and its distribution and hazard function. Some general
properties of these estimators are derived from two characterizations. It is
shown that the rate of convergence with respect to supremum norm on a compact
interval for the density and hazard rate estimator is at least
and typically , whereas the difference
between the empirical and estimated distribution function vanishes with rate
under certain regularity assumptions.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ141 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm), Version 3 is
the extended technical report cited in version
Gibbs point process approximation: Total variation bounds using Stein's method
We obtain upper bounds for the total variation distance between the
distributions of two Gibbs point processes in a very general setting.
Applications are provided to various well-known processes and settings from
spatial statistics and statistical physics, including the comparison of two
Lennard-Jones processes, hard core approximation of an area interaction process
and the approximation of lattice processes by a continuous Gibbs process. Our
proof of the main results is based on Stein's method. We construct an explicit
coupling between two spatial birth-death processes to obtain Stein factors, and
employ the Georgii-Nguyen-Zessin equation for the total bound.Comment: Published in at http://dx.doi.org/10.1214/13-AOP895 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Bounds for the probability generating functional of a Gibbs point process
We derive explicit lower and upper bounds for the probability generating
functional of a stationary locally stable Gibbs point process, which can be
applied to summary statistics like the F function. For pairwise interaction
processes we obtain further estimates for the G and K functions, the intensity
and higher order correlation functions. The proof of the main result is based
on Stein's method for Poisson point process approximation.Comment: 15 page
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