258 research outputs found
Bayesian Neural Tree Models for Nonparametric Regression
Frequentist and Bayesian methods differ in many aspects, but share some basic
optimal properties. In real-life classification and regression problems,
situations exist in which a model based on one of the methods is preferable
based on some subjective criterion. Nonparametric classification and regression
techniques, such as decision trees and neural networks, have frequentist
(classification and regression trees (CART) and artificial neural networks) as
well as Bayesian (Bayesian CART and Bayesian neural networks) approaches to
learning from data. In this work, we present two hybrid models combining the
Bayesian and frequentist versions of CART and neural networks, which we call
the Bayesian neural tree (BNT) models. Both models exploit the architecture of
decision trees and have lesser number of parameters to tune than advanced
neural networks. Such models can simultaneously perform feature selection and
prediction, are highly flexible, and generalize well in settings with a limited
number of training observations. We study the consistency of the proposed
models, and derive the optimal value of an important model parameter. We also
provide illustrative examples using a wide variety of real-life regression data
sets
Controlling the degree of caution in statistical inference with the Bayesian and frequentist approaches as opposite extremes
In statistical practice, whether a Bayesian or frequentist approach is used
in inference depends not only on the availability of prior information but also
on the attitude taken toward partial prior information, with frequentists
tending to be more cautious than Bayesians. The proposed framework defines that
attitude in terms of a specified amount of caution, thereby enabling data
analysis at the level of caution desired and on the basis of any prior
information. The caution parameter represents the attitude toward partial prior
information in much the same way as a loss function represents the attitude
toward risk. When there is very little prior information and nonzero caution,
the resulting inferences correspond to those of the candidate confidence
intervals and p-values that are most similar to the credible intervals and
hypothesis probabilities of the specified Bayesian posterior. On the other
hand, in the presence of a known physical distribution of the parameter,
inferences are based only on the corresponding physical posterior. In those
extremes of either negligible prior information or complete prior information,
inferences do not depend on the degree of caution. Partial prior information
between those two extremes leads to intermediate inferences that are more
frequentistic to the extent that the caution is high and more Bayesian to the
extent that the caution is low
Resolving conflicts between statistical methods by probability combination: Application to empirical Bayes analyses of genomic data
In the typical analysis of a data set, a single method is selected for
statistical reporting even when equally applicable methods yield very different
results. Examples of equally applicable methods can correspond to those of
different ancillary statistics in frequentist inference and of different prior
distributions in Bayesian inference. More broadly, choices are made between
parametric and nonparametric methods and between frequentist and Bayesian
methods.
Rather than choosing a single method, it can be safer, in a game-theoretic
sense, to combine those that are equally appropriate in light of the available
information. Since methods of combining subjectively assessed probability
distributions are not objective enough for that purpose, this paper introduces
a method of distribution combination that does not require any assignment of
distribution weights. It does so by formalizing a hedging strategy in terms of
a game between three players: nature, a statistician combining distributions,
and a statistician refusing to combine distributions. The optimal move of the
first statistician reduces to the solution of a simpler problem of selecting an
estimating distribution that minimizes the Kullback-Leibler loss maximized over
the plausible distributions to be combined. The resulting combined distribution
is a linear combination of the most extreme of the distributions to be combined
that are scientifically plausible. The optimal weights are close enough to each
other that no extreme distribution dominates the others.
The new methodology is illustrated by combining conflicting empirical Bayes
methodologies in the context of gene expression data analysis
DIAMONDS: a new Bayesian Nested Sampling tool. Application to Peak Bagging of solar-like oscillations
To exploit the full potential of Kepler light curves, sophisticated and
robust analysis tools are now required more than ever. Characterizing single
stars with an unprecedented level of accuracy and subsequently analyzing
stellar populations in detail are fundamental to further constrain stellar
structure and evolutionary models. We developed a new code, termed Diamonds,
for Bayesian parameter estimation and model comparison by means of the nested
sampling Monte Carlo (NSMC) algorithm, an efficient and powerful method very
suitable for high-dimensional and multi-modal problems. A detailed description
of the features implemented in the code is given with a focus on the novelties
and differences with respect to other existing methods based on NSMC. Diamonds
is then tested on the bright F8 V star KIC~9139163, a challenging target for
peak-bagging analysis due to its large number of oscillation peaks observed,
which are coupled to the blending that occurs between peaks, and the
strong stellar background signal. We further strain the performance of the
approach by adopting a 1147.5 days-long Kepler light curve. The Diamonds code
is able to provide robust results for the peak-bagging analysis of KIC~9139163.
We test the detection of different astrophysical backgrounds in the star and
provide a criterion based on the Bayesian evidence for assessing the peak
significance of the detected oscillations in detail. We present results for 59
individual oscillation frequencies, amplitudes and linewidths and provide a
detailed comparison to the existing values in the literature. Lastly, we
successfully demonstrate an innovative approach to peak bagging that exploits
the capability of Diamonds to sample multi-modal distributions, which is of
great potential for possible future automatization of the analysis technique.Comment: 22 pages, 14 figures, 3 tables. Accepted for publication in A&
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