References of "Ley, Christophe 50024038"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailThe Wasserstein Impact Measure (WIM): A practical tool for quantifying prior impact in Bayesian statistics
Ley, Christophe UL; Ghaderinezhad, Fatemeh; Serrien, Ben

in Computational Statistics and Data Analysis (2022), 174

The prior distribution is a crucial building block in Bayesian analysis, and its choice will impact the subsequent inference. It is therefore important to have a convenient way to quantify this impact, as ... [more ▼]

The prior distribution is a crucial building block in Bayesian analysis, and its choice will impact the subsequent inference. It is therefore important to have a convenient way to quantify this impact, as such a measure of prior impact will help to choose between two or more priors in a given situation. To this end a new approach, the Wasserstein Impact Measure (WIM), is introduced. In three simulated scenarios, the WIM is compared to two competitor prior impact measures from the literature, and its versatility is illustrated via two real datasets. [less ▲]

Detailed reference viewed: 17 (1 UL)
Full Text
See detailUsing Bayes factors to compare dynamical models of hydrological systems
Mingo Ndiwago, Damian UL; Nijzink, Remko; Ley, Christophe UL et al

Scientific Conference (2022, June 05)

Detailed reference viewed: 19 (3 UL)
Full Text
Peer Reviewed
See detailComing Together of Bayesian Inference and Skew Spherical Data
Ley, Christophe UL; Nakhaei Rad, Najmeh; Bekker, Andriette et al

in Frontiers in Big Data (2022)

This paper presents Bayesian directional data modeling via the skew-rotationally-symmetric Fisher-von Mises-Langevin (FvML) distribution. The prior distributions for the parameters are a pivotal building ... [more ▼]

This paper presents Bayesian directional data modeling via the skew-rotationally-symmetric Fisher-von Mises-Langevin (FvML) distribution. The prior distributions for the parameters are a pivotal building block in Bayesian analysis, therefore, the impact of the proposed priors will be quantified using the Wasserstein Impact Measure (WIM) to guide the practitioner in the implementation process. For the computation of the posterior, modifications of Gibbs and slice samplings are applied for generating samples. We demonstrate the applicability of our contribution via synthetic and real data analyses. Our investigation paves the way for Bayesian analysis of skew circular and spherical data. [less ▲]

Detailed reference viewed: 12 (0 UL)
Full Text
Peer Reviewed
See detailHow injury registration and preseason assessment are being delivered : an international survey of sports physical therapists
Ley, Christophe UL; Mendonça, Luciana D.; Schuermans, Joke et al

in Physical Therapy in Sport (2022), 53

Objective To identify the role of sports physical therapists (PT) in the organization of injury registration and preseason assessment, applied in athletic organizations and sports teams of different ... [more ▼]

Objective To identify the role of sports physical therapists (PT) in the organization of injury registration and preseason assessment, applied in athletic organizations and sports teams of different gender and level world-wide. Design cross-sectional study. Setting LimeSurvey platform. Participants Sports PTs working with athletes invited through International Federation of Sports Physical Therapy. Main outcome measures injury registration and athlete's screening. Results 414 sports PTs participated in this international survey (mean age of 37.66 (SD = 9.38) years). 340 participants indicated that the PT as the responsible for injury registration. Barriers to properly register injury throughout the season were indicated by 157 sports PT and 86 (54.77%) indicated a lack of time on their routine as the main factor. 93 participants (30.09%) indicated that they customize the prevention program based on the preseason assessment. Sports PTs who reported not performing a preseason assessment (92 participants - 22.22%) mainly indicated this to be consequence of lack of structure in the organization (44 participants – 47.82%). Conclusion The majority of the sports PTs participate on injury registration and perform preseason assessment in athletes. However, lack of time in their routine and structure in the organization were recognized as the most important barriers to organize these properly. [less ▲]

Detailed reference viewed: 9 (0 UL)
Full Text
Peer Reviewed
See detailHow injury prevention programs are being structured and implemented worldwide: An international survey of sports physical therapists
Ley, Christophe UL; Mendonça, Luciana D.; Schuermans, Joke et al

in Physical Therapy in Sport (2022), 53

Objective To identify the role of sports physical therapists (PT) in the injury prevention process and to compare the structure of preventive programs and associated (organization) policies applied in ... [more ▼]

Objective To identify the role of sports physical therapists (PT) in the injury prevention process and to compare the structure of preventive programs and associated (organization) policies applied in athletic organizations and sports teams of varying gender and level world-wide. Design: cross-sectional study. Setting LimeSurvey platform. Participants Sports PT working with athletes invited through the International Federation of Sports Physical Therapy. Main outcome measures Sports injury prevention program (IPP) structure and implementation. Results 414 participants fully participate in this survey study. Athlete's injury history (68.84%), the most common injuries within the sport modality (67.87%) and athlete's preseason screening results (64.01%) were most frequently used to customize IPPs. Warm-up (70.04%) and individually PT-guided exercise-therapy (70.04%) were the preferred methods to organize the prevention routine. The main barrier for IPP implementation was lack of time within the athlete's weekly training schedule (66.66%). The majority of the participants (72.84%) reported to evaluate the perception of IPP's effect by comparing current and preceding seasons' injury occurrences. Conclusion These survey results are the first identifying contemporary sports injury prevention organization and implementation policies on an international level. This information might support the sports PT community in improving and standardizing IPP (implementation) strategies worldwide. [less ▲]

Detailed reference viewed: 14 (0 UL)
Full Text
Peer Reviewed
See detailArtificial intelligence and machine learning: an introduction for orthopaedic surgeons
Ley, Christophe UL; Martin, R. Kyle; Pareek, Ayoosh et al

in Knee Surgery, Sports Traumatology, Arthroscopy (2021)

The application of artificial intelligence (AI) and machine learning to the field of orthopaedic surgery is rapidly increasing. While this represents an important step in the advancement of our specialty ... [more ▼]

The application of artificial intelligence (AI) and machine learning to the field of orthopaedic surgery is rapidly increasing. While this represents an important step in the advancement of our specialty, the concept of AI is rich with statistical jargon and techniques unfamiliar to many clinicians. This knowledge gap may limit the impact and potential of these novel techniques. We aim to narrow this gap in a way that is accessible for all orthopaedic surgeons. With this manuscript, we introduce the concept of AI and machine learning and give examples of how it can impact clinical practice and patient care. [less ▲]

Detailed reference viewed: 15 (0 UL)
Full Text
Peer Reviewed
See detailThe Safety of Bilateral Simultaneous Hip and Knee Arthroplasty versus Staged Arthroplasty in a High-Volume Center Comparing Blood Loss, Peri- and Postoperative Complications, and Early Functional Outcome
Ley, Christophe UL; Najfeld, Michael; Kalteis, Thomas et al

in Journal of Clinical Medicine (2021)

Purpose: In recent years, there has been increasing interest in the use of simultaneous hip and knee arthroplasty compared to staged procedures in patients with bilateral pathology. The aim of this study ... [more ▼]

Purpose: In recent years, there has been increasing interest in the use of simultaneous hip and knee arthroplasty compared to staged procedures in patients with bilateral pathology. The aim of this study was to compare simultaneous and staged hip and knee arthroplasty in patients with bilateral pathology by assessing the transfusion rate, postoperative hemoglobin drop, length of stay (LOS), in-hospital complications, 30-day readmissions and early functional outcome. Methods: We conducted a retrospective cohort study that included all patients who were undergoing primary TKA, THA and UKA by a single surgeon in a high-volume arthroplasty center between 2015 and 2020 as simultaneous or staged procedures. Staged bilateral arthroplasties were performed within 12 months and were stratified by the time between procedures. Data were acquired through the electronic files at the Orthopädische Chirurgie München (OCM). For functional outcome, the ability of the patients to walk independently on the ward was compared with the ability to walk a set of stairs alone, which was recorded daily by the attending physiotherapist. Results: In total n = 305 patients were assessed for eligibility and included in this study. One hundred and forty-five patients were allocated to the staged arthroplasty group. This group was subdivided into a hip and a knee group, whereas the knee group was split into TKA and UKA. The second staged procedure was performed within 12 months of the first procedure. One hundred and sixty patients were allocated to the simultaneous arthroplasty group. This group was also subdivided into a hip and knee group, whereas the knee group was split again into a TKA and UKA group. No statistical difference was found between the two groups regarding demographic data. Primary outcome measurements: There was no significant difference in the transfusion rate or complication rate. Secondarily, no statistically significant difference was found between the postoperative hemoglobin drop and the functional outcome, or in the length of stay (LOS) between both groups. Walking the stairs showed a significant difference in the knee group. Conclusions: There were no significant differences observed in the transfusion rate in-hospital complications, or readmission rate between both groups. The early functional outcome showed no significant difference in mobility for all groups. Simultaneous arthroplasty for knee or hip is as safe as a staged procedure, with no higher risk for the patient, in a specialized high-volume center. Level of evidence: Level IV. [less ▲]

Detailed reference viewed: 15 (0 UL)
Full Text
Peer Reviewed
See detailElliptical Symmetry Tests in R
Ley, Christophe UL; Babić, Slad̄ana; Palangetić, Marko

in R Journal (2021), 13:2

The assumption of elliptical symmetry has an important role in many theoretical develop ments and applications. Hence, it is of primary importance to be able to test whether that assumption actually holds ... [more ▼]

The assumption of elliptical symmetry has an important role in many theoretical develop ments and applications. Hence, it is of primary importance to be able to test whether that assumption actually holds true or not. Various tests have been proposed in the literature for this problem. To the best of our knowledge, none of them has been implemented in R. This article describes the R package elliptical symmetry which implements several well-known tests for elliptical symmetry together with some recent tests. We demonstrate the testing procedures with a real data example. [less ▲]

Detailed reference viewed: 12 (0 UL)
Full Text
Peer Reviewed
See detailSome simple variance bounds from Stein’s method
Ley, Christophe UL; Daly, Fraser; Ghaderinezhad, Fatemeh et al

in ALEA: Latin American Journal of Probability and Mathematical Statistics (2021), 18

Using coupling techniques based on Stein’s method for probability approximation, we revisit classical variance bounding inequalities of Chernoff, Cacoullos, Chen and Klaassen. Our bounds are immediate in ... [more ▼]

Using coupling techniques based on Stein’s method for probability approximation, we revisit classical variance bounding inequalities of Chernoff, Cacoullos, Chen and Klaassen. Our bounds are immediate in any context wherein a Stein identity is available. After providing illustrative examples for a Gaussian and a Gumbel target distribution, our main contributions are new variance bounds in settings where the underlying density function is unknown or intractable. Applications include bounds for analysis of the posterior in Bayesian statistics, bounds for asymptotically Gaussian random variables using zero-biased couplings, and bounds for random variables which are New Better (Worse) than Used in Expectation. [less ▲]

Detailed reference viewed: 14 (0 UL)
Full Text
Peer Reviewed
See detailThe Probabilistic Final Standing Calculator: a fair stochastic tool to handle abruptly stopped football seasons
Ley, Christophe UL; Van Eetvelde, Hans; Magnus Hvattum, Lars

in AStA Advances in Statistical Analysis (2021)

The COVID-19 pandemic has left its marks in the sports world, forcing the full stop of all sports-related activities in the first half of 2020. Football leagues were suddenly stopped, and each country was ... [more ▼]

The COVID-19 pandemic has left its marks in the sports world, forcing the full stop of all sports-related activities in the first half of 2020. Football leagues were suddenly stopped, and each country was hesitating between a relaunch of the competition and a premature ending. Some opted for the latter option and took as the final standing of the season the ranking from the moment the competition got interrupted. This decision has been perceived as unfair, especially by those teams who had remaining matches against easier opponents. In this paper, we introduce a tool to calculate in a fairer way the final standings of domestic leagues that have to stop prematurely: our Probabilistic Final Standing Calculator (PFSC). It is based on a stochastic model taking into account the results of the matches played and simulating the remaining matches, yielding the probabilities for the various possible final rankings. We have compared our PFSC with state-of-the-art prediction models, using previous seasons which we pretend to stop at different points in time. We illustrate our PFSC by showing how a probabilistic ranking of the French Ligue 1 in the stopped 2019–2020 season could have led to alternative, potentially fairer, decisions on the final standing. [less ▲]

Detailed reference viewed: 10 (0 UL)
Full Text
Peer Reviewed
See detailWhen the score function is the identity function - A tale of characterizations of the normal distribution
Ley, Christophe UL

in Econometrics and Statistics (2020)

The normal distribution is well-known for several results that it is the only to fulfil. Much less well-known is the fact that many of these characterizations follow from the fact that the derivative of ... [more ▼]

The normal distribution is well-known for several results that it is the only to fulfil. Much less well-known is the fact that many of these characterizations follow from the fact that the derivative of the log-density of the normal distribution is the (negative) identity function. This a priori very simple yet surprising observation allows a deeper understanding of existing characterizations and paves the way for an immediate extension of various seemingly normal-based characterizations to a general density by replacing the (negative) identity function in these results with the derivative of that log-density. [less ▲]

Detailed reference viewed: 10 (2 UL)
Full Text
Peer Reviewed
See detailSine-skewed toroidal distributions and their application in protein bioinformatics
Ley, Christophe UL; Ameijeiras-Alonso, Jose

in Biostatistics (2020)

In the bioinformatics field, there has been a growing interest in modeling dihedral angles of amino acids by viewing them as data on the torus. This has motivated, over the past years, new proposals of ... [more ▼]

In the bioinformatics field, there has been a growing interest in modeling dihedral angles of amino acids by viewing them as data on the torus. This has motivated, over the past years, new proposals of distributions on the torus. The main drawback of most of these models is that the related densities are (pointwise) symmetric, despite the fact that the data usually present asymmetric patterns. This motivates the need to find a new way of constructing asymmetric toroidal distributions starting from a symmetric distribution. We tackle this problem in this article by introducing the sine-skewed toroidal distributions. The general properties of the new models are derived. Based on the initial symmetric model, explicit expressions for the shape and dependence measures are obtained, a simple algorithm for generating random numbers is provided, and asymptotic results for the maximum likelihood estimators are established. An important feature of our construction is that no extra normalizing constant needs to be calculated, leading to more flexible distributions without increasing the complexity of the models. The benefit of employing these new sine-skewed toroidal distributions is shown on the basis of protein data, where, in general, the new models outperform their symmetric antecedents. [less ▲]

Detailed reference viewed: 10 (0 UL)
See detailScience Meets Sports: When Statistics Are More Than Numbers
Ley, Christophe UL; Dominicy, Yves

Book published by Cambridge Scholars Publishing (2020)

This book presents the field of sports statistics to two very distinct target audiences, namely academicians, in order to raise their interest in this growing field, and, on the other hand, sports fans ... [more ▼]

This book presents the field of sports statistics to two very distinct target audiences, namely academicians, in order to raise their interest in this growing field, and, on the other hand, sports fans, who, even without advanced mathematical knowledge, will be able to understand the data analysis and gain new insights into their favourite sports. The book thus offers a unique perspective on this attractive topic by combining sports analytics, data visualisation and advanced statistical procedures to extract new findings from sports data such as improved rankings or prediction methods. Bringing together insights from football, tennis, basketball, track and field, and baseball, the book will appeal to aficionados of any sport, and, thanks to its cutting-edge data analysis tools, will provide the reader with completely new insights into their favourite sport in an engaging and user-friendly way. [less ▲]

Detailed reference viewed: 9 (0 UL)
See detailApplied Directional Statistics : Modern Methods and Case Studies
Ley, Christophe UL; Verdebout, Thomas

Book published by Chapman and Hall/CRC (2019)

This book collects important advances in methodology and data analysis for directional statistics. It is the companion book of the more theoretical treatment presented in Modern Directional Statistics ... [more ▼]

This book collects important advances in methodology and data analysis for directional statistics. It is the companion book of the more theoretical treatment presented in Modern Directional Statistics (CRC Press, 2017). The field of directional statistics has received a lot of attention due to demands from disciplines such as life sciences or machine learning, the availability of massive data sets requiring adapted statistical techniques, and technological advances. This book covers important progress in bioinformatics, biology, astrophysics, oceanography, environmental sciences, earth sciences, machine learning and social sciences. [less ▲]

Detailed reference viewed: 10 (0 UL)
See detailModern Directional Statistics
Ley, Christophe UL; Verdebout, Thomas

Book published by Chapman and Hall/CRC (2017)

Modern Directional Statistics collects important advances in methodology and theory for directional statistics over the last two decades. It provides a detailed overview and analysis of recent results ... [more ▼]

Modern Directional Statistics collects important advances in methodology and theory for directional statistics over the last two decades. It provides a detailed overview and analysis of recent results that can help both researchers and practitioners. Knowledge of multivariate statistics eases the reading but is not mandatory. The field of directional statistics has received a lot of attention over the past two decades, due to new demands from domains such as life sciences or machine learning, to the availability of massive data sets requiring adapted statistical techniques, and to technological advances. This book covers important progresses in distribution theory, high-dimensional statistics, kernel density estimation, efficient inference on directional supports, and computational and graphical methods. [less ▲]

Detailed reference viewed: 12 (0 UL)