21,330 research outputs found
Evaluating hedge fund performance: a stochastic dominance approach
We introduce a general and flexible framework for hedge fund performance evaluation and asset allocation: stochastic dominance (SD) theory. Our approach utilizes statistical tests for stochastic dominance to compare the returns of hedge funds. We form hedge fund portfolios by using SD criteria and examine the out-of-sample performance of these hedge fund portfolios. Compared to performance of portfolios of randomly selected hedge funds and mean-variance e¢ cient hedge funds, our results show that fund selection method based on SD criteria greatly improves the performance of hedge fund portfolio
Convexity and a sum-product type estimate
In this paper we further study the relationship between convexity and
additive growth, building on the work of Schoen and Shkredov (\cite{SS}) to get
some improvements to earlier results of Elekes, Nathanson and Ruzsa
(\cite{ENR}). In particular, we show that for any finite set
and any strictly convex or concave function ,
and For the latter of
these inequalities, we go on to consider the consequences for a sum-product
type problem
Isochores Merit the Prefix 'Iso'
The isochore concept in human genome sequence was challenged in an analysis
by the International Human Genome Sequencing Consortium (IHGSC). We argue here
that a statement in IGHSC analysis concerning the existence of isochore is
incorrect, because it had applied an inappropriate statistical test. To test
the existence of isochores should be equivalent to a test of homogeneity of
windowed GC%. The statistical test applied in the IHGSC's analysis, the
binomial test, is however a test of a sequence being random on the base level.
For testing the existence of isochore, or homogeneity in GC%, we propose to use
another statistical test: the analysis of variance (ANOVA). It can be shown
that DNA sequences that are rejected by binomial test may not be rejected by
the ANOVA test.Comment: 14 pages (including 1 figure), submitte
Local Linear Fitting Under Near Epoch Dependence: Uniform consistency with Convergence Rates
Local linear fitting is a popular nonparametric method in statistical and econometric modelling. Lu and Linton (2007) established the pointwise asymptotic distribution for the local linear estimator of a nonparametric regression function under the condition of near epoch dependence. In this paper, we further investigate the uniform consistency of this estimator. The uniform strong and weak consistencies with convergence rates for the local linear fitting are established under mild conditions. Furthermore, general results regarding uniform convergence rates for nonparametric kernel-based estimators are provided. The results of this paper will be of wide potential interest in time series semiparametric modelling.α-mixing, local linear fitting, near epoch dependence, convergence rates, uniform consistency
Visual7W: Grounded Question Answering in Images
We have seen great progress in basic perceptual tasks such as object
recognition and detection. However, AI models still fail to match humans in
high-level vision tasks due to the lack of capacities for deeper reasoning.
Recently the new task of visual question answering (QA) has been proposed to
evaluate a model's capacity for deep image understanding. Previous works have
established a loose, global association between QA sentences and images.
However, many questions and answers, in practice, relate to local regions in
the images. We establish a semantic link between textual descriptions and image
regions by object-level grounding. It enables a new type of QA with visual
answers, in addition to textual answers used in previous work. We study the
visual QA tasks in a grounded setting with a large collection of 7W
multiple-choice QA pairs. Furthermore, we evaluate human performance and
several baseline models on the QA tasks. Finally, we propose a novel LSTM model
with spatial attention to tackle the 7W QA tasks.Comment: CVPR 201
An improved sum-product estimate for general finite fields
This paper improves on a sum-product estimate obtained by Katz and Shen for
subsets of a finite field whose order is not prime
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