283,829 research outputs found
Regression Models and Experimental Designs: A Tutorial for Simulation Analaysts
This tutorial explains the basics of linear regression models. especially low-order polynomials. and the corresponding statistical designs. namely, designs of resolution III, IV, V, and Central Composite Designs (CCDs).This tutorial assumes 'white noise', which means that the residuals of the fitted linear regression model are normally, independently, and identically distributed with zero mean.The tutorial gathers statistical results that are scattered throughout the literature on mathematical statistics, and presents these results in a form that is understandable to simulation analysts.metamodels;fractional factorial designs;Plackett-Burman designs;factor interactions;validation;cross-validation
Experimental investigation of consumer price evaluations
We develop a procedure to collect experimental choice data for estimating consumer preferences with a special focus on consumer price evaluations. For this purpose we employ a heteroskedastic mixed logit model that measures the effect of the way prices are specified on the variance of choice. Our procedure is based on optimal design ideas from the statistics literature and on some algorithms for constructing choice designs published in marketing journals. In an empirical application on mobile phone preferences we find evidence that the way prices are specified significantly affects the variance of choice. In a simulation study we show that our design is significantly more efficient than randomly generated designs., which can be regarded as equivalent to most commonly used experimental designs in the literature.heterogeneity;Bayesian design;demand;quasi-random;task complexity
Stochastic Gradient Bayesian Optimal Experimental Designs for Simulation-based Inference
Simulation-based inference (SBI) methods tackle complex scientific models
with challenging inverse problems. However, SBI models often face a significant
hurdle due to their non-differentiable nature, which hampers the use of
gradient-based optimization techniques. Bayesian Optimal Experimental Design
(BOED) is a powerful approach that aims to make the most efficient use of
experimental resources for improved inferences. While stochastic gradient BOED
methods have shown promising results in high-dimensional design problems, they
have mostly neglected the integration of BOED with SBI due to the difficult
non-differentiable property of many SBI simulators. In this work, we establish
a crucial connection between ratio-based SBI inference algorithms and
stochastic gradient-based variational inference by leveraging mutual
information bounds. This connection allows us to extend BOED to SBI
applications, enabling the simultaneous optimization of experimental designs
and amortized inference functions. We demonstrate our approach on a simple
linear model and offer implementation details for practitioners.Comment: Presented at ICML 2023 workshop on Differentiable Everythin
Helical channel design and technology for cooling of muon beams
Novel magnetic helical channel designs for capture and cooling of bright muon
beams are being developed using numerical simulations based on new inventions
such as helical solenoid (HS) magnets and hydrogen-pressurized RF (HPRF)
cavities. We are close to the factor of a million six-dimensional phase space
(6D) reduction needed for muon colliders. Recent experimental and simulation
results are presented.Comment: 6 pp. 14th Advanced Accelerator Concepts Workshop 13-19 Jun 2010:
Annapolis, Marylan
An experimental evaluation of a loop versus a reference design for two-channel microarrays
Motivation: Despite theoretical arguments that socalled "loop designs" of two-channel DNA microarray experiments are more efficient, biologists keep on using "reference designs". We describe two sets of microarray experiments with RNA from two different biological systems (TPA-stimulated mammalian cells and Streptomyces coelicor). In each case, both a loop and a reference design were performed using the same RNA preparations with the aim to study their relative efficiency. Results: The results of these experiments show that (1) the loop design attains a much higher precision than the reference design, (2) multiplicative spot effects are a large source of variability, and if they are not accounted for in the mathematical model, for example by taking log-ratios or including spot-effects, then the model will perform poorly. The first result is reinforced by a simulation study. Practical recommendations are given on how simple loop designs can be extended to more realistic experimental designs and how standard statistical methods allow the experimentalist to use and interpret the results from loop designs in practice
Simulation of non-linear bearing forces for post-stability investigation
Different types of bearing designs were developed to improve dynamic properties of rotor-bearing systems. Elliptical bearings, multisleeve bearings, tilting pad and other designs such as herringbone groove were utilized to increase resistance to the onset of self excited vibrations. Experimental trials are costly, two alternative methods are used to gain a qualitative insight. The first one creates mathematical model and applies both a digital or an analog computer simulation. The second one investigates phenomena occurring on the laboratory rig with the bearing replaced by an electronic simulating device, working in a feedback loop, which produces forces,which are functions of journal displacement and velocity. The simulated hydrodynamic forces are produced according to assumed characteristics matched to the bearing type. The principal benefit of the analog simulation is that nonlinear characteristics of a subsystem are precisely identified and mathematical methods applied for a wide class of problems are checked on the experimental installation
Validation of the GATE Monte Carlo simulation platform for modelling a CsI(Tl) scintillation camera dedicated to small animal imaging
Monte Carlo simulations are increasingly used in scintigraphic imaging to
model imaging systems and to develop and assess tomographic reconstruction
algorithms and correction methods for improved image quantitation. GATE (GEANT
4 Application for Tomographic Emission) is a new Monte Carlo simulation
platform based on GEANT4 dedicated to nuclear imaging applications. This paper
describes the GATE simulation of a prototype of scintillation camera dedicated
to small animal imaging and consisting of a CsI(Tl) crystal array coupled to a
position sensitive photomultiplier tube. The relevance of GATE to model the
camera prototype was assessed by comparing simulated 99mTc point spread
functions, energy spectra, sensitivities, scatter fractions and image of a
capillary phantom with the corresponding experimental measurements. Results
showed an excellent agreement between simulated and experimental data:
experimental spatial resolutions were predicted with an error less than 100 mu
m. The difference between experimental and simulated system sensitivities for
different source-to-collimator distances was within 2%. Simulated and
experimental scatter fractions in a [98-182 keV] energy window differed by less
than 2% for sources located in water. Simulated and experimental energy spectra
agreed very well between 40 and 180 keV. These results demonstrate the ability
and flexibility of GATE for simulating original detector designs. The main
weakness of GATE concerns the long computation time it requires: this issue is
currently under investigation by the GEANT4 and the GATE collaboration
Experimental designs for multiple-level responses, with application to a large-scale educational intervention
Educational research often studies subjects that are in naturally clustered
groups of classrooms or schools. When designing a randomized experiment to
evaluate an intervention directed at teachers, but with effects on teachers and
their students, the power or anticipated variance for the treatment effect
needs to be examined at both levels. If the treatment is applied to clusters,
power is usually reduced. At the same time, a cluster design decreases the
probability of contamination, and contamination can also reduce power to detect
a treatment effect. Designs that are optimal at one level may be inefficient
for estimating the treatment effect at another level. In this paper we study
the efficiency of three designs and their ability to detect a treatment effect:
randomize schools to treatment, randomize teachers within schools to treatment,
and completely randomize teachers to treatment. The three designs are compared
for both the teacher and student level within the mixed model framework, and a
simulation study is conducted to compare expected treatment variances for the
three designs with various levels of correlation within and between clusters.
We present a computer program that study designers can use to explore the
anticipated variances of treatment effects under proposed experimental designs
and settings.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS216 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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