Search results for " Probability"
showing 10 items of 2176 documents
Simulating term structure of interest rates with arbitrary marginals
2011
Decision models under uncertainty rely their analysis on scenarios of the economic factors. A key economic factor is the term structure of interest rates (yields). Simulation models of the yield curve usually assume that the conjugate distribution of the interest rates is lognormal. Dynamic models, like vector auto-regression, implicitly postulate that the logarithm of the interest rates is normally distributed. Statistical analyses have, however, shown that stationary transformations (yield changes) of the interest rates are substantially leptokurtic, thus posing serious doubts on the reliability of the available models. We propose in this paper a VARTA model (Biller and Nelson, 2003) to s…
Variable length Markov chains and dynamical sources
2010
Infinite random sequences of letters can be viewed as stochastic chains or as strings produced by a source, in the sense of information theory. The relationship between Variable Length Markov Chains (VLMC) and probabilistic dynamical sources is studied. We establish a probabilistic frame for context trees and VLMC and we prove that any VLMC is a dynamical source for which we explicitly build the mapping. On two examples, the ``comb'' and the ``bamboo blossom'', we find a necessary and sufficient condition for the existence and the unicity of a stationary probability measure for the VLMC. These two examples are detailed in order to provide the associated Dirichlet series as well as the gener…
Using time-varying transition probabilities in Markov switching processes to adjust US fiscal policy for asset prices
2013
This paper tests for nonlinear effects of asset prices on the US fiscal policy. By modeling government spending and taxes as time-varying transition probability Markovian processes (TVPMS), we find that taxes significantly adjust in a nonlinear fashion to asset prices. In particular, taxes respond to housing and (to a smaller extent) to stock price changes during normal times. However, at periods characterized by high financial volatility, government taxation only counteracts stock market developments (and not the dynamics of the housing sector). As for government spending, it is neutral vis-a-vis the asset market cycles. We conclude that, correcting the fiscal balance and, notably, the rev…
Nonlinear effects of asset prices on fiscal policy: Evidence from the UK, Italy and Spain
2015
"Available online 1 August 2014"
The fundamental theory of optimal "Anti-Bayesian" parametric pattern classification using order statistics criteria
2013
Author's version of an article in the journal: Pattern Recognition. Also available from the publisher at: http://dx.doi.org/10.1016/j.patcog.2012.07.004 The gold standard for a classifier is the condition of optimality attained by the Bayesian classifier. Within a Bayesian paradigm, if we are allowed to compare the testing sample with only a single point in the feature space from each class, the optimal Bayesian strategy would be to achieve this based on the (Mahalanobis) distance from the corresponding means. The reader should observe that, in this context, the mean, in one sense, is the most central point in the respective distribution. In this paper, we shall show that we can obtain opti…
Differential models of twin correlations in skew for body-mass index (BMI)
2018
Background Body Mass Index (BMI), like most human phenotypes, is substantially heritable. However, BMI is not normally distributed; the skew appears to be structural, and increases as a function of age. Moreover, twin correlations for BMI commonly violate the assumptions of the most common variety of the classical twin model, with the MZ twin correlation greater than twice the DZ correlation. This study aimed to decompose twin correlations for BMI using more general skew-t distributions. Methods Same sex MZ and DZ twin pairs (N = 7,086) from the community-based Washington State Twin Registry were included. We used latent profile analysis (LPA) to decompose twin correlations for BMI into mul…
Sample size planning of two-arm superiority and noninferiority survival studies with discrete follow-up
2016
In clinical trials using lifetime as primary outcome variable, it is more the rule than the exception that even for patients who are failing in the course of the study, survival time does not become known exactly since follow-up takes place according to a restricted schedule with fixed, possibly long intervals between successive visits. In practice, the discreteness of the data obtained under such circumstances is plainly ignored both in data analysis and in sample size planning of survival time studies. As a framework for analyzing the impact of making no difference between continuous and discrete recording of failure times, we use a scenario in which the partially observed times are assig…
Prognostic Implications of the Complement Protein C1q in Gliomas
2019
The contribution of the complement system in the pathophysiology of brain cancers has been recently considered in light of its well-known involvement in carcinogenesis. Complement system represents an important component of the inflammatory response, which acts as a functional bridge between the innate and adaptive immune response. C1q, the first recognition subcomponent of the complement classical pathway, has recently been shown to be involved in a range of pathophysiological functions that are not dependent on complement activation. C1q is expressed in the microenvironment of various types of human tumors, including melanoma, prostate, mesothelioma, and ovarian cancers, where it can exer…
Genetic discontinuity between local hunter-gatherers and central Europe's first farmers.
2009
Cultivating Farmers Were the ancestors of modern Europeans the local hunter-gatherers who assimilated farming practices from neighboring cultures, or were they farmers who migrated from the Near East in the early Neolithic? By analyzing ancient hunter-gatherer skeletal DNA from 2300 to 13,400 B.C.E. Bramanti et al. (p. 137 , published online 3 September) investigated the genetic relationship of European Ice Age hunter-gatherers, the first farmers of Europe, and modern Europeans. The results reject the hypothesis of direct continuity between hunter-gatherers and early farmers and between hunter-gatherers and modern Europeans. Major parts of central and northern Europe were colonized by incom…
The Link Between Local Recurrence and Distant Metastases in Patients With Rectal Cancer.
2019
BACKGROUND/AIM The relationships between local recurrence (LR), the development of distant metastases (DM) and prognosis in patients with rectal cancer remain unclear. PATIENTS AND METHODS In 606 patients who underwent curative resection, the role of LR was assessed retrospectively by time-dependent multivariate Cox models with inverse probability of treatment weighting taking into account competing risks. RESULTS Patients with LR had more DM than patients without LR (49/79, 62% vs. 86/524, 16.4%; p<0.001); 37% of LR-associated DM developed before or at LR, 63% after diagnosis of LR. Fifty-five percent of patients without DM at diagnosis of LR later developed DM. In these patients, the inci…