Search results for "Large sample"
showing 10 items of 50 documents
On the hidden side of liquidity
2012
This paper deals with the informativeness of iceberg orders, also known as hidden limit orders (HLOs). Namely, we analyze how the market reacts when the presence of hidden volume in the limit order book is revealed by the trading process. We use high frequency book and transaction data from the Spanish Stock Exchange, including a large sample of executed HLOs. We show that just when hidden volume is detected, traders on the opposite side of the market become more aggressive, exploiting the opportunity to consume more than expected at the best quotes. However, neither illiquidity nor volatility increases in the short-term. Furthermore, the detection of hidden volume has no relevant price imp…
A comparison of two indirect methods for estimating average levels of gene flow using microsatellite data.
1999
We compare the performance of Nm estimates based on FST and RST obtained from microsatellite data using simulations of the stepwise mutation model with range constraints in allele size classes. The results of the simulations suggest that the use of microsatellite loci can lead to serious overestimations of Nm, particularly when population sizes are large (N5000) and range constraints are high (K20). The simulations also indicate that, when population sizes are small (N/= 500) and migration rates are moderate (Nm approximately 2), violations to the assumption used to derive the Nm estimators lead to biased results. Under ideal conditions, i.e. large sample sizes (ns/= 50) and many loci (nl/=…
Problematic and non-problematic engagement in Online Sexual Activities across the lifespan
2021
During the last decade, the number of people using the Internet for sexual purposes has increased exponentially. However, most studies conducted so far have analysed Online Sexual Activity (OSA) of adolescents and young people, meaning that we have few information on how this phenomenon is expressed across the lifespan. The aim of this study was to analyse three aspects of OSA (prevalence of different OSAs, motives to engage in OSA, and excessive and problematic engagement in OSA) in a large sample of individuals in different developmental stages. A self-selected sample of 8040 individuals between 12 and 85 years old were recruited and completed an online survey. Participants were distribut…
MALDI-TOF mass spectrometry identification of filamentous fungi in the clinical laboratory.
2014
Pôle MERS F. Dalle; International audience; This study aimed to validate the effectiveness of a standardised procedure for the MALDI-TOF mass spectrometry (MS)-based identification on a large sample of filamentous fungi routinely identified in university hospitals' laboratories. Non-dermatophyte filamentous fungi prospectively isolated in the routine activity of five teaching hospitals in France were first identified by conventional methods in each laboratory and then by MS in one centre. DNA sequence-based identification resolved discrepancies between both methods. In this study, of the 625 analysed filamentous fungi of 58 species, 501 (80%) and 556 (89%) were correctly identified by conve…
Stabilization of asthma prevalence among adolescents and increase among schoolchildren (ISAAC phases I and III) in Spain.
2004
Background: Most studies show a steep increase in asthma prevalence in the last decades, although few studies had applied the same methodology. Recent reports point out the possibility that the epidemic has come to an end. We have studied the prevalence of asthma in a very large sample of children, repeating the study eight years apart. Methods: Repeated cross-sectional studies using the International Study of Asthma and Allergies in Childhood (ISAAC) protocol in a sample of Spanish schoolchildren 6–7 (parent-reported) and 13–14 (self-reported) years old in 1994–95 (phase I) and 2002–2003 (phase III). The number of participants was 42 417 in phase I and 42 813 in phase III. The participat…
Sprint mechanical variables in elite athletes: Are force-velocity profiles sport specific or individual?
2019
Purpose The main aim of this investigation was to quantify differences in sprint mechanical variables across sports and within each sport. Secondary aims were to quantify sex differences and relationships among the variables. Methods In this cross-sectional study of elite athletes, 235 women (23 ± 5 y and 65 ± 7 kg) and 431 men (23 ± 4 y and 80 ± 12 kg) from 23 different sports (including 128 medalists from World Championships and/or Olympic Games) were tested in a 40-m sprint at the Norwegian Olympic Training Center between 1995 and 2018. These were pre-existing data from quarterly or semi-annual testing that the athletes performed for training purposes. Anthropometric and speed-time sprin…
Prevalence and Profile of Mild Cognitive Impairment in Parkinson’s Disease
2011
<i>Background/Aims:</i> The frequency of mild cognitive impairment (MCI) in Parkinson’s disease (PD) ranges from 19 to 40%, and this is probably due to methodological differences between the studies. The aim of this study was to evaluate the frequency and profile of MCI in a large sample of nondemented PD subjects and neurologically healthy subjects (NHS). <i>Methods:</i> A total of 872 subjects (582 controls and 290 PD) were included. The association between MCI and PD was tested, using logistic regression models; odds ratios (OR) with 95% confidence intervals (CI) were calculated. <i>Results:</i> Fifty-three percent of PD subjects and 45% NHS met the cr…
Export Barriers and Strategic Grouping
2007
Abstract The purpose of our work is to investigate the export strategy of international business by explicitly comparing exporting firms with non-exporting ones. This task has been undertaken by having recourse to a very large sample with more than 55,000 registered Spanish enterprises from all commercial sectors. Using this sample, we try to demonstrate that exporters and non-exporters belong to different strategic groups, with different profit levels. The existence of three kinds of barriers (managerial, organisational and external) constrains migration of non-exporting enterprises to the exporting group. However, the conclusions herein presented point at some ways of avoiding these barri…
Stability and surgical complications of tooth-borne and bone-borne appliances in surgical assisted rapid maxillary expansion: a systematic review
2021
The objective of this systematic review was to evaluate the stability and complications of tooth-borne (TB), bone-borne (BB) and hybrid (TB-BB) appliances in surgically assisted rapid maxillary expansion (SARME). Database searches were conducted (PubMed, Embase, Cochrane Library and SciELO), as well as a grey literature search (Google Scholar) and hand searches of reference lists. Forty-six articles were included after study selection (κ=0.854). After eligibility assessment, 16 articles and one article from the grey literature were processed (κ=0.866) and six articles were selected by hand searching, for a total of 23 articles included. Regarding stability, TB appliances showed width relaps…
Use of Quantitative Morphological Analysis Combined with a Large Sample Size for Estimating Morphological Variability in a Case Study of Armoured Mit…
2015
Abstract The morphology of Oribatida and similar little-known groups of organisms varies considerably, which complicates morphological analysis (e.g. species descriptions). Qualitative analyses have been carried out mostly on a small number of individuals (n < 25). There is lack of studies dealing with mechanisms of how that variation can change in relation to sample size and insufficient discussion on whether qualitative or quantitative analysis is more appropriate for description of morphological variability. A total of 500 adult Carabodes subarcticus Trägårdh, 1902 Oribatida were collected from a local population. Six qualitative and six quantitative traits were characterised using li…