Persona: Pérez Martín, Jorge
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Pérez Martín
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Jorge
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Publicación Cost-effectiveness analysis with new models of artificial intelligence. Medical applications(Universidad Nacional de Educación a Distancia (España). Escuela Internacional de Doctorado. Programa de Doctorado en Sistemas Inteligentes, 2019) Pérez Martín, Jorge; Díez Vegas, Francisco JavierPublicación La infraestructura de la calidad para apoyar la contratación pública sostenible(2024) Massó Aguado, Daniel; Arbeloa Losada, Marta; García López, Paloma; Pérez Martín, JorgePublicación El papel de los consumidores para alcanzar los ODS(2024) Massó Aguado, Daniel; Arbeloa Losada, Marta; García López, Paloma; Pérez Martín, JorgePublicación OpenMarkov, an Open-Source Tool for Probabilistic Graphical Models(International Joint Conference on Artificial Intelligence, 2019) Arias Calleja, Manuel; Pérez Martín, Jorge; Luque Gallego, Manuel; Díez Vegas, Francisco JavierOpenMarkov is a Java open-source tool for creating and evaluating probabilistic graphical models, including Bayesian networks, influence diagrams, and some Markov models. With more than 100,000 lines of code, it offers some features for interactive learning, explanation of reasoning, and cost-effectiveness analysis, which are not available in any other tool. OpenMarkov has been used at universities, research centers, and large companies in more than 30 countries on four continents. Several models, some of them for real-world medical applications, built with OpenMarkov, are publicly available on Internet.Publicación Evaluation of Markov models with discontinuities(Society for Medical Decision Making, 2019-02-07) Bermejo, Iñigo; Pérez Martín, Jorge; Díez Vegas, Francisco JavierBackground. Several methods, such as the half-cycle correction and the life-table method, were developed to attenuate the error introduced in Markov models by the discretization of time. Elbasha and Chhatwal have proposed alternative “corrections” based on numerical integration techniques. They present an example whose results suggest that the trapezoidal rule, which is equivalent to the half-cycle correction, is not as accurate as Simpson’s 1/3 and 3/8 rules. However, they did not take into consideration the impact of discontinuities. Objective. To propose a method for evaluating Markov models with discontinuities. Design. Applying the trapezoidal rule, we derive a method that consists of adjusting the model by setting the cost at each point of discontinuity to the mean of the left and right limits of the cost function. We then take from the literature a model with a cycle length of 1 year and a discontinuity on the cost function and compare our method with other “corrections” using as the gold standard an equivalent model with a cycle length of 1 day. Results. As expected, for this model, the life-table method is more accurate than assuming that transitions occur at the beginning or the end of cycles. The application of numerical integration techniques without taking into account the discontinuity causes large errors. The model with averaged cost values yields very small errors, especially for the trapezoidal and the 1/3 Simpson rules. Conclusion. In the case of discontinuities, we recommend applying the trapezoidal rule on an averaged model because this method has a mathematical justification, and in our empirical evaluation, it was more accurate than the sophisticated 3/8 Simpson rule.Publicación Assessment of Video Accessibility by Students of a MOOC on Digital Materials for All(Institute of Electrical and Electronics Engineers, 2021-05-21) Elisa M. Molanes López; Rodríguez Ascaso, Alejandro; Letón Molina, Emilio; Pérez Martín, Jorge; https://orcid.org/0000-0003-3217-8551The assessment of multimedia accessibility is a relevant, complex and time-consuming task, which takes more than simply checking whether the video has audiodescription and captions or not. In our study, we face this challenge through the: 1) involvement of a cohort of novice evaluators, who previously took part in a MOOC on the accessibility of digital content and 2) the division of the accessibility assessment into the application of a set of criteria. Two groups of novice accessibility testers were asked to evaluate the accessibility of two similar videos, one video per group. While both videos were equivalent in terms of their pedagogical content, only one of them had non-severe accessibility barriers for people with low vision and for blind people. Each participant was asked to rate qualitatively a set of statements extracted from the WCAG 2.1 success criteria, one generic statement about the video accessibility, and a set of statements on the quality perception and the aspects of personal preference. The largest differences in ratings occurred for statements whose success criteria had been improved. It was also the case for one success criterion that is understandable but hardly applicable by novice evaluators, according to the literature. However, the difference was statistically significant only for the success criterion with more salient differences between both videos. As a main conclusion, a group of novice evaluators can identify accessibility problems in videos when using specific accessibility statements.Publicación Markov influence diagrams: a graphical tool for cost-effectiveness analysis(Society for Medical Decision Making, 2017-01-11) Yebra, Mar; Bermejo, Iñigo; Palacios Alonso, Miguel Ángel; Arias Calleja, Manuel; Luque Gallego, Manuel; Pérez Martín, Jorge; Díez Vegas, Francisco JavierMarkov influence diagrams (MIDs) are a new type of probabilistic graphical models that extend influence diagrams in the same way as Markov decision trees extend decision trees. They have been designed to build state-transition models, mainly in medicine, and perform cost-effectiveness analysis. Using a causal graph that may contain several variables per cycle, MIDs can model various features of the patient without multiplying the number of states; in particular, they can represent the history of the patient without using tunnel states. OpenMarkov, an open-source tool, allows the decision analyst to build and evaluate MIDs—including cost-effectiveness analysis and several types of deterministic and probabilistic sensitivity analysis—with a graphical user interface, without writing any code. This way, MIDs can be used to easily build and evaluate complex models whose implementation as spreadsheets or decision trees would be cumbersome or unfeasible in practice. Furthermore, many problems that previously required discrete event simulation can be solved with MIDs, i.e., within the paradigm of state-transition models, in which many health economists feel more comfortable.Publicación Cost-effectiveness of Pediatric Bilateral Cochlear Implantation in Spain(Wiley Online Library, 2017) Artaso, Miguel A.; Díez Vegas, Francisco Javier; Pérez Martín, JorgeObjective: To determine the incremental cost-effectiveness of bilateral versus unilateral cochlear implantation for one-year-old children suffering from bilateral sensorineural severe to profound hearing loss from the perspective of the Spanish public health system. Study Design: Cost-utility analysis. Methods: We conducted a general-population survey to estimate the quality of life increase contributed by the second implant. We built a Markov influence diagram and evaluated it for a life-long time horizon with a 3% discount rate in the base case. Results: The incremental cost-effectiveness ratio (ICER) of simultaneous bilateral implantation with respect to unilateral implantation for one-year-old children with severe to profound deafness is €10,323 per quality-adjusted life year (QALY). For sequential bilateral implantation, it rises to €11,733/QALY. Both options are cost-effective for the Spanish health system, whose willingness to pay is estimated at around €30,000/QALY. The probabilistic sensitivity analysis shows that the probability of bilateral implantation being cost-effective reaches 100% for that cost-effectiveness threshold. Conclusions: Bilateral implantation is clearly cost-effective for the population considered. If possible, it should be done simultaneously, i.e., in one surgical operation, because it is as safe and effective as sequential implantation, and saves costs for the system and for users and their families. Sequential implantation is also cost-effective for children who have received the first implant recently, but it is difficult to determine when it ceases to be so because of the lack of detailed data. These results are specific for Spain but the model can easily be adapted to other countries. Level of Evidence: 2CPublicación Quality of the captions produced by students of an accessibility MOOC using a semi-automatic tool(Springer Nature, 2020-07-05) Pérez Martín, Jorge; Rodríguez Ascaso, Alejandro; Molanes-López, Elisa M.; https://orcid.org/0000-0003-3217-8551Some people have problems accessing multimedia services available on the web. Contributions to accessibility made by end users who lack institutional support in the design, production or deployment of media accommodations should be considered. The aim of our paper is to assess the quality of the captions produced using YouTube by non-professional subtitlers who only received basic training. We also identify potential improvements either in the subtitling tool or in the training resources, which could enhance the quality of the captions. We conducted a study in which 53 participants of a MOOC on digital accessibility used the automatic speech recognition (ASR) feature of YouTube to produce the captions for a video provided by the teaching staff. We assessed the quality of the captions produced by the students and then compared it with the quality of the captions produced by: (a) a human expert and (b) the ASR-based subtitling by YouTube. Students’ errors occurred mainly in the number of characters per line, the speed of the captions, failing to use a new line per participant, and not including sound effects. The course should warn students to use a new line per participant, teach them how to subtitle sound effects, specify the maximum number of characters per line of text, and inform that in some countries such as Spain, captions can be edited but in other countries this may not be possible. Our recommendations for the YouTube editor include improving both the user interface and the ASR, with a view to enhancing ongoing and future research.Publicación Teaching Probabilistic Graphical Models with OpenMarkov(MDPI, 2022-11-30) Díez Vegas, Francisco Javier; Arias Calleja, Manuel; Pérez Martín, Jorge; Luque Gallego, ManuelOpenMarkov is an open-source software tool for probabilistic graphical models. It has been developed especially for medicine, but has also been used to build applications in other fields and for tuition, in more than 30 countries. In this paper we explain how to use it as a pedagogical tool to teach the main concepts of Bayesian networks and influence diagrams, such as conditional dependence and independence, d-separation, Markov blankets, explaining away, optimal policies, expected utilities, etc., and some inference algorithms: logic sampling, likelihood weighting, and arc reversal. The facilities for learning Bayesian networks interactively can be used to illustrate step by step the performance of the two basic algorithms: search-and-score and PC.