Directed Networks
Informative Neural Ensemble Kalman Learning
Trautner, Margaret, Margolis, Gabriel, Ravela, Sai
In stochastic systems, informative approaches select key measurement or decision variables that maximize information gain to enhance the efficacy of model-related inferences. Neural Learning also embodies stochastic dynamics, but informative Learning is less developed. Here, we propose Informative Ensemble Kalman Learning, which replaces backpropagation with an adaptive Ensemble Kalman Filter to quantify uncertainty and enables maximizing information gain during Learning. After demonstrating Ensemble Kalman Learning's competitive performance on standard datasets, we apply the informative approach to neural structure learning. In particular, we show that when trained from the Lorenz-63 system's simulations, the efficaciously learned structure recovers the dynamical equations. To the best of our knowledge, Informative Ensemble Kalman Learning is new. Results suggest that this approach to optimized Learning is promising.
Competence-Based Student Modelling with Dynamic Bayesian Networks
Morales-Gamboa, Rafael, Sucar, L. Enrique
Competences have grown in popularity in the western educational world [1, 2, 3], and so the interest on developing computational models for competences that can be used to support a variety of educational processes, from creating digital catalogues of competences to course design to monitoring competence development by students. Although meaning varies among organisations, in this paper we will assume a definition of competence along the line of'the capability of someone to act effectively in some kind of situations, which demands the mobilization of a variety of internal and external resources' which broadly integrates aspects of external performance and internal composition of competences that emerge in the literature. Research in this area is important because little information is available regarding what competences the students have developed along their studies, and to what extend, beyond the stated learning objectives of the educational programmes they are subscribed in, and the titles of the courses they have taken and passed. Furthermore, information regarding the development of competences do not accumulate, neither at school nor later in life. For example, transversal competences are develop along many courses on specific contexts (e.g.
Differentiable TAN Structure Learning for Bayesian Network Classifiers
Roth, Wolfgang, Pernkopf, Franz
Learning the structure of Bayesian networks is a difficult combinatorial optimization problem. In this paper, we consider learning of tree-augmented naive Bayes (TAN) structures for Bayesian network classifiers with discrete input features. Instead of performing a combinatorial optimization over the space of possible graph structures, the proposed method learns a distribution over graph structures. After training, we select the most probable structure of this distribution. This allows for a joint training of the Bayesian network parameters along with its TAN structure using gradient-based optimization. The proposed method is agnostic to the specific loss and only requires that it is differentiable. We perform extensive experiments using a hybrid generative-discriminative loss based on the discriminative probabilistic margin. Our method consistently outperforms random TAN structures and Chow-Liu TAN structures.
Amortized learning of neural causal representations
Ke, Nan Rosemary, Wang, Jane. X., Mitrovic, Jovana, Szummer, Martin, Rezende, Danilo J.
Causal models can compactly and efficiently encode the data-generating process under all interventions and hence may generalize better under changes in distribution. These models are often represented as Bayesian networks and learning them scales poorly with the number of variables. Moreover, these approaches cannot leverage previously learned knowledge to help with learning new causal models. In order to tackle these challenges, we represent a novel algorithm called \textit{causal relational networks} (CRN) for learning causal models using neural networks. The CRN represent causal models using continuous representations and hence could scale much better with the number of variables. These models also take in previously learned information to facilitate learning of new causal models. Finally, we propose a decoding-based metric to evaluate causal models with continuous representations. We test our method on synthetic data achieving high accuracy and quick adaptation to previously unseen causal models.
A Practical Introduction to Bayesian Estimation of Causal Effects: Parametric and Nonparametric Approaches
Oganisian, Arman, Roy, Jason A.
Substantial advances in Bayesian methods for causal inference have been developed in recent years. We provide an introduction to Bayesian inference for causal effects for practicing statisticians who have some familiarity with Bayesian models and would like an overview of what it can add to causal estimation in practical settings. In the paper, we demonstrate how priors can induce shrinkage and sparsity on parametric models and be used to perform probabilistic sensitivity analyses around causal assumptions. We provide an overview of nonparametric Bayesian estimation and survey their applications in the causal inference literature. Inference in the point-treatment and time-varying treatment settings are considered. For the latter, we explore both static and dynamic treatment regimes. Throughout, we illustrate implementation using off-the-shelf open source software. We hope the reader will walk away with implementation-level knowledge of Bayesian causal inference using both parametric and nonparametric models. All synthetic examples and code used in the paper are publicly available on a companion GitHub repository.
From Optimizing Engagement to Measuring Value
Milli, Smitha, Belli, Luca, Hardt, Moritz
Most recommendation engines today are based on predicting user engagement, e.g. predicting whether a user will click on an item or not. However, there is potentially a large gap between engagement signals and a desired notion of "value" that is worth optimizing for. We use the framework of measurement theory to (a) confront the designer with a normative question about what the designer values, (b) provide a general latent variable model approach that can be used to operationalize the target construct and directly optimize for it, and (c) guide the designer in evaluating and revising their operationalization. We implement our approach on the Twitter platform on millions of users. In line with established approaches to assessing the validity of measurements, we perform a qualitative evaluation of how well our model captures a desired notion of "value".
Would Bayesian approaches improve COVID-19 forecasts?
Modelling for the pandemic has shown that this debate should still be front and center. The frequentists are mostly in the spotlight advising world leaders. If you listen close you will hear a common refrain'we just need more data.' This is, of course, the age-old problem of statistical significance. However, today, we aren't in a harmless lab study, these data are only realized through death.
NLP For WhatsApp Chats
Natural Language Processing or NLP is a field of Artificial Intelligence which focuses on enabling the systems for understanding and processing the human languages. In this article, I will use NLP to analyze my WhatsApp Chats. For some privacy reasons, I will use Person 1, Person 2 and so on in my WhatsApp Chats. If you have never exported your whatsapp chats before, don't worry it's very easy. For NLP of WhatsApp chats, you need to extract the whatsapp chats from your smartphone.
Assessing Safety-Critical Systems from Operational Testing: A Study on Autonomous Vehicles
Zhao, Xingyu, Salako, Kizito, Strigini, Lorenzo, Robu, Valentin, Flynn, David
Context: Demonstrating high reliability and safety for safety-critical systems (SCSs) remains a hard problem. Diverse evidence needs to be combined in a rigorous way: in particular, results of operational testing with other evidence from design and verification. Growing use of machine learning in SCSs, by precluding most established methods for gaining assurance, makes operational testing even more important for supporting safety and reliability claims. Objective: We use Autonomous Vehicles (AVs) as a current example to revisit the problem of demonstrating high reliability. AVs are making their debut on public roads: methods for assessing whether an AV is safe enough are urgently needed. We demonstrate how to answer 5 questions that would arise in assessing an AV type, starting with those proposed by a highly-cited study. Method: We apply new theorems extending Conservative Bayesian Inference (CBI), which exploit the rigour of Bayesian methods while reducing the risk of involuntary misuse associated with now-common applications of Bayesian inference; we define additional conditions needed for applying these methods to AVs. Results: Prior knowledge can bring substantial advantages if the AV design allows strong expectations of safety before road testing. We also show how naive attempts at conservative assessment may lead to over-optimism instead; why extrapolating the trend of disengagements is not suitable for safety claims; use of knowledge that an AV has moved to a less stressful environment. Conclusion: While some reliability targets will remain too high to be practically verifiable, CBI removes a major source of doubt: it allows use of prior knowledge without inducing dangerously optimistic biases. For certain ranges of required reliability and prior beliefs, CBI thus supports feasible, sound arguments. Useful conservative claims can be derived from limited prior knowledge.