Search results for " Statistical"
showing 10 items of 1649 documents
The effect of round-off error on long memory processes
2011
We study how the round-off (or discretization) error changes the statistical properties of a Gaussian long memory process. We show that the autocovariance and the spectral density of the discretized process are asymptotically rescaled by a factor smaller than one, and we compute exactly this scaling factor. Consequently, we find that the discretized process is also long memory with the same Hurst exponent as the original process. We consider the properties of two estimators of the Hurst exponent, namely the local Whittle (LW) estimator and the Detrended Fluctuation Analysis (DFA). By using analytical considerations and numerical simulations we show that, in presence of round-off error, both…
Measuring consumers’ level of satisfaction for online food shopping during COVID-19 in Italy using POSETs
2021
Abstract The pandemic COVID 19 has upset the economic, social, financial, and general behavioral systems. Global crisis has a large impact overall and related fallouts significantly affect existent structural paradigms in every country and region across the world. In particular, the spread of COVID-19 pandemic has led to having to rethink the way we produce and consume food. Within this global change, a rise in the number of consumers who purchase food products online in order to comply with the rules aimed at limiting the circulation of the virus should be emphasized. Consequently, probably causing a long-term positive effect on m-commerce. The purpose is to elaborate on the index of the s…
Biometric analysis of Brachionus plicatilis ecotypes from Spanish lagoons
1983
Univariate comparisons and several multivariate statistical analyses have been performed to study the morphometric variability of B. plicatilis. Both laboratory clones kept under constant conditions and natural populations from different Spanish lagoons and different times of the year have been compared. The results show that not only size, but also allometric coefficients are influenced by environmental factors. However, an important genetic component in the variation of shape and size has been visualized. A clear North-South ordination of the populations of the different lagoons and an important dispersion between their summer populations as well as great differences due to seasonal varia…
Compensation of missing wedge effects with sequential statistical reconstruction in electron tomography.
2014
Electron tomography (ET) of biological samples is used to study the organization and the structure of the whole cell and subcellular complexes in great detail. However, projections cannot be acquired over full tilt angle range with biological samples in electron microscopy. ET image reconstruction can be considered an ill-posed problem because of this missing information. This results in artifacts, seen as the loss of three-dimensional (3D) resolution in the reconstructed images. The goal of this study was to achieve isotropic resolution with a statistical reconstruction method, sequential maximum a posteriori expectation maximization (sMAP-EM), using no prior morphological knowledge about …
A Web Application for Interactive Visualization of European Basketball Data
2020
The statistical analysis of basketball games is a fast-growing field. Certainly, basketball data are scientifically relevant because an appropriate analysis provides a great deal of information about the performance of both players and teams. The number of games played each season generates a large amount of data worth analyzing. Basketball analytics is well established in U.S. leagues. In Europe, however, it has not been duly developed. This study focuses on the top three European team competitions: the EuroLeague, the EuroCup, and the Spanish ACB (Association of Basketball Clubs, acronym in Spanish) league. Their official websites provide access to game data for anyone who is interested, …
A systematic review of maternal smoking during pregnancy and fetal measurements with meta-analysis
2017
Maternal smoking during pregnancy is linked to reduced birth weight but the gestation at onset of this relationship is not certain. We present a systematic review of the literature describing associations between maternal smoking during pregnancy and ultrasound measurements of fetal size, together with an accompanying meta-analysis. Studies were selected from electronic databases (OVID, EMBASE and Google Scholar) that examined associations between maternal smoking or smoke exposure and antenatal fetal ultrasound measurements. Outcome measures were first, second or third trimester fetal measurements. There were 284 abstracts identified, 16 papers were included in the review and the meta-anal…
You cannot speak and listen at the same time: a probabilistic model of turn-taking.
2017
Turn-taking is a preverbal skill whose mastering constitutes an important precondition for many social interactions and joint actions. However, the cognitive mechanisms supporting turn-taking abilities are still poorly understood. Here, we propose a computational analysis of turn-taking in terms of two general mechanisms supporting joint actions: action prediction (e.g., recognizing the interlocutor's message and predicting the end of turn) and signaling (e.g., modifying one's own speech to make it more predictable and discriminable). We test the hypothesis that in a simulated conversational scenario dyads using these two mechanisms can recognize the utterances of their co-actors faster, wh…
Contribution to the platoon distribution analysis in steady-state traffic conditions
2014
The traffic flow analysis and the relevant vehicle distribution (“free-moving” or “platooned” vehicles) on highway facilities at uninterrupted flow has always had fundamental importance in Highway Engineering, with special reference to topics like traffic operations, car accidents, road safety and air pollution emissions. In light of this, the study suggests a calculation algorithm as a random test generator to simulate a steady state traffic flow and to provide time headways. Thanks to the outcome produced by numerical simulations, we analysed platoon distributions within traffic flows in a steady-state regime and showed the results of numerical analyses carried out by traffic random proce…
Foaming in membrane bioreactors: Identification of the causes
2012
Membrane bioreactors (MBRs) represent by now a well established alternative for wastewater treatment. Their increasing development is undoubtedly related to the several advantages that such technology is able to guarantee. Nevertheless, this technology is not exempt from operational problems; among them the foaming still represents an "open challenge" of the MBR field, due to the high complexity of phenomenon. Unfortunately, very little work has been done on the foaming in MBRs and further studies are required. Actually, there is not a distinct difference between conventional activated system and MBR: the main difference is that the MBR plants can retain most Extracellular Polymeric Substan…
Dietary acrylamide and physical performance tests: A cross-sectional analysis
2021
Background Dietary acrylamide is found in certain foods, such as deep frying, baking and roasting, and is associated with higher inflammatory and oxidative stress parameters. The association between dietary acrylamide and physical performance has not yet been explored. The aim of the study was to investigate the relationship between dietary acrylamide intake and physical performance tests in a large cohort of North American individuals affected by knee osteoarthritis or at high risk for this condition. Methods Dietary acrylamide intake was obtained through a food frequency questionnaire and reported in quartiles and as an increase in deciles. Physical performance was explored using the 20-…