4,483 research outputs found
Predicting Paid Certification in Massive Open Online Courses
Massive open online courses (MOOCs) have been proliferating because of the free or low-cost offering of content for learners, attracting the attention of many stakeholders across the entire educational landscape. Since 2012, coined as “the Year of the MOOCs”, several platforms have gathered millions of learners in just a decade. Nevertheless, the certification rate of both free and paid courses has been low, and only about 4.5–13% and 1–3%, respectively, of the total number of enrolled learners obtain a certificate at the end of their courses. Still, most research concentrates on completion, ignoring the certification problem, and especially its financial aspects. Thus, the research described in the present thesis aimed to investigate paid certification in MOOCs, for the first time, in a comprehensive way, and as early as the first week of the course, by exploring its various levels. First, the latent correlation between learner activities and their paid certification decisions was examined by (1) statistically comparing the activities of non-paying learners with course purchasers and (2) predicting paid certification using different machine learning (ML) techniques. Our temporal (weekly) analysis showed statistical significance at various levels when comparing the activities of non-paying learners with those of the certificate purchasers across the five courses analysed. Furthermore, we used the learner’s activities (number of step accesses, attempts, correct and wrong answers, and time spent on learning steps) to build our paid certification predictor, which achieved promising balanced accuracies (BAs), ranging from 0.77 to 0.95. Having employed simple predictions based on a few clickstream variables, we then analysed more in-depth what other information can be extracted from MOOC interaction (namely discussion forums) for paid certification prediction. However, to better explore the learners’ discussion forums, we built, as an original contribution, MOOCSent, a cross- platform review-based sentiment classifier, using over 1.2 million MOOC sentiment-labelled reviews. MOOCSent addresses various limitations of the current sentiment classifiers including (1) using one single source of data (previous literature on sentiment classification in MOOCs was based on single platforms only, and hence less generalisable, with relatively low number of instances compared to our obtained dataset;) (2) lower model outputs, where most of the current models are based on 2-polar
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classifier (positive or negative only); (3) disregarding important sentiment indicators, such as emojis and emoticons, during text embedding; and (4) reporting average performance metrics only, preventing the evaluation of model performance at the level of class (sentiment). Finally, and with the help of MOOCSent, we used the learners’ discussion forums to predict paid certification after annotating learners’ comments and replies with the sentiment using MOOCSent. This multi-input model contains raw data (learner textual inputs), sentiment classification generated by MOOCSent, computed features (number of likes received for each textual input), and several features extracted from the texts (character counts, word counts, and part of speech (POS) tags for each textual instance). This experiment adopted various deep predictive approaches – specifically that allow multi-input architecture - to early (i.e., weekly) investigate if data obtained from MOOC learners’ interaction in discussion forums can predict learners’ purchase decisions (certification). Considering the staggeringly low rate of paid certification in MOOCs, this present thesis contributes to the knowledge and field of MOOC learner analytics with predicting paid certification, for the first time, at such a comprehensive (with data from over 200 thousand learners from 5 different discipline courses), actionable (analysing learners decision from the first week of the course) and longitudinal (with 23 runs from 2013 to 2017) scale. The present thesis contributes with (1) investigating various conventional and deep ML approaches for predicting paid certification in MOOCs using learner clickstreams (Chapter 5) and course discussion forums (Chapter 7), (2) building the largest MOOC sentiment classifier (MOOCSent) based on learners’ reviews of the courses from the leading MOOC platforms, namely Coursera, FutureLearn and Udemy, and handles emojis and emoticons using dedicated lexicons that contain over three thousand corresponding explanatory words/phrases, (3) proposing and developing, for the first time, multi-input model for predicting certification based on the data from discussion forums which synchronously processes the textual (comments and replies) and numerical (number of likes posted and received, sentiments) data from the forums, adapting the suitable classifier for each type of data as explained in detail in Chapter 7
Explainable text-based features in predictive models of crowdfunding campaigns
Reward-Based Crowdfunding offers an opportunity for innovative ventures that would not be supported through traditional financing. A key problem for those seeking funding is understanding which features of a crowdfunding campaign will sway the decisions of a sufficient number of funders. Predictive models of fund-raising campaigns used in combination with Explainable AI methods promise to provide such insights. However, previous work on Explainable AI has largely focused on quantitative structured data. In this study, our aim is to construct explainable models of human decisions based on analysis of natural language text, thus contributing to a fast-growing body of research on the use of Explainable AI for text analytics. We propose a novel method to construct predictions based on text via semantic clustering of sentences, which, compared with traditional methods using individual words and phrases, allows complex meaning contained in the text to be operationalised. Using experimental evaluation, we compare our proposed method to keyword extraction and topic modelling, which have traditionally been used in similar applications. Our results demonstrate that the sentence clustering method produces features with significant predictive power, compared to keyword-based methods and topic models, but which are much easier to interpret for human raters. We furthermore conduct a SHAP analysis of the models incorporating sentence clusters, demonstrating concrete insights into the types of natural language content that influence the outcome of crowdfunding campaigns
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Mitigating Data Scarcity for Neural Language Models
In recent years, pretrained neural language models (PNLMs) have taken the field of natural language processing by storm, achieving new benchmarks and state-of-theart performances. These models often rely heavily on annotated data, which may not always be available. Data scarcity are commonly found in specialized domains, such as medical, or in low-resource languages that are underexplored by AI research. In this dissertation, we focus on mitigating data scarcity using data augmentation and neural ensemble learning techniques for neural language models. In both research directions, we implement neural network algorithms and evaluate their impact on assisting neural language models in downstream NLP tasks. Specifically, for data augmentation, we explore two techniques: 1) creating positive training data by moving an answer span around its original context and 2) using text simplification techniques to introduce a variety of writing styles to the original training data. Our results indicate that these simple and effective solutions improve the performance of neural language models considerably in low-resource NLP domains and tasks. For neural ensemble learning, we use a multi-label neural classifier to select the best prediction outcome from a variety of individual pretrained neural language models trained for a low-resource medical text simplification task
Explanation Strategies for Image Classification in Humans vs. Current Explainable AI
Explainable AI (XAI) methods provide explanations of AI models, but our
understanding of how they compare with human explanations remains limited. In
image classification, we found that humans adopted more explorative attention
strategies for explanation than the classification task itself. Two
representative explanation strategies were identified through clustering: One
involved focused visual scanning on foreground objects with more conceptual
explanations diagnostic for inferring class labels, whereas the other involved
explorative scanning with more visual explanations rated higher for
effectiveness. Interestingly, XAI saliency-map explanations had the highest
similarity to the explorative attention strategy in humans, and explanations
highlighting discriminative features from invoking observable causality through
perturbation had higher similarity to human strategies than those highlighting
internal features associated with higher class score. Thus, humans differ in
information and strategy use for explanations, and XAI methods that highlight
features informing observable causality match better with human explanations,
potentially more accessible to users
Low- and high-resource opinion summarization
Customer reviews play a vital role in the online purchasing decisions we make. The reviews
express user opinions that are useful for setting realistic expectations and uncovering important
details about products. However, some products receive hundreds or even thousands of
reviews, making them time-consuming to read. Moreover, many reviews contain uninformative
content, such as irrelevant personal experiences. Automatic summarization offers an
alternative – short text summaries capturing the essential information expressed in reviews.
Automatically produced summaries can reflect overall or particular opinions and be tailored to
user preferences. Besides being presented on major e-commerce platforms, home assistants
can also vocalize them. This approach can improve user satisfaction by assisting in making
faster and better decisions.
Modern summarization approaches are based on neural networks, often requiring thousands of
annotated samples for training. However, human-written summaries for products are expensive
to produce because annotators need to read many reviews. This has led to annotated data
scarcity where only a few datasets are available. Data scarcity is the central theme of our
works, and we propose a number of approaches to alleviate the problem. The thesis consists
of two parts where we discuss low- and high-resource data settings.
In the first part, we propose self-supervised learning methods applied to customer reviews
and few-shot methods for learning from small annotated datasets. Customer reviews without
summaries are available in large quantities, contain a breadth of in-domain specifics, and
provide a powerful training signal. We show that reviews can be used for learning summarizers
via a self-supervised objective. Further, we address two main challenges associated with
learning from small annotated datasets. First, large models rapidly overfit on small datasets
leading to poor generalization. Second, it is not possible to learn a wide range of in-domain
specifics (e.g., product aspects and usage) from a handful of gold samples. This leads to
subtle semantic mistakes in generated summaries, such as ‘great dead on arrival battery.’ We
address the first challenge by explicitly modeling summary properties (e.g., content coverage
and sentiment alignment). Furthermore, we leverage small modules – adapters – that are
more robust to overfitting. As we show, despite their size, these modules can be used to
store in-domain knowledge to reduce semantic mistakes. Lastly, we propose a simple method
for learning personalized summarizers based on aspects, such as ‘price,’ ‘battery life,’ and
‘resolution.’ This task is harder to learn, and we present a few-shot method for training a
query-based summarizer on small annotated datasets.
In the second part, we focus on the high-resource setting and present a large dataset with
summaries collected from various online resources. The dataset has more than 33,000 humanwritten
summaries, where each is linked up to thousands of reviews. This, however, makes it
challenging to apply an ‘expensive’ deep encoder due to memory and computational costs. To
address this problem, we propose selecting small subsets of informative reviews. Only these
subsets are encoded by the deep encoder and subsequently summarized. We show that the
selector and summarizer can be trained end-to-end via amortized inference and policy gradient
methods
Robustness Analysis of Video-Language Models Against Visual and Language Perturbations
Joint visual and language modeling on large-scale datasets has recently shown
good progress in multi-modal tasks when compared to single modal learning.
However, robustness of these approaches against real-world perturbations has
not been studied. In this work, we perform the first extensive robustness study
of video-language models against various real-world perturbations. We focus on
text-to-video retrieval and propose two large-scale benchmark datasets,
MSRVTT-P and YouCook2-P, which utilize 90 different visual and 35 different
text perturbations. The study reveals some interesting initial findings from
the studied models: 1) models are generally more susceptible when only video is
perturbed as opposed to when only text is perturbed, 2) models that are
pre-trained are more robust than those trained from scratch, 3) models attend
more to scene and objects rather than motion and action. We hope this study
will serve as a benchmark and guide future research in robust video-language
learning. The benchmark introduced in this study along with the code and
datasets is available at https://bit.ly/3CNOly4.Comment: NeurIPS 2022 Datasets and Benchmarks Track. This projects webpage is
located at https://bit.ly/3CNOly
Neural Concept-to-text Generation with Knowledge Graphs
Modern language models are strong at generating grammatically correct, natural lan- guage. However, they still struggle with commonsense reasoning - a task involving making inferences about common everyday situations without explicitly stated informa- tion. Prior research into the topic has shown that providing additional information from external sources helps language models generate better outputs. In this thesis, we explore methods of extracting information from knowledge graphs and using it as additional input for a pre-trained generative language model. We do this by either extracting a subgraph relevant to the context or by using graph neural networks to predict which information is relevant. Moreover, we experiment with a post-editing approach and with a model trained in a multi-task setup (generation and consistency classification). Our methods are evaluated on the CommonGen benchmark for generative commonsense reasoning using both automatic metrics and a detailed error analysis on a small sample of outputs. We show that the methods improve over a simple language model fine-tuning baseline, although they do not set a new state of the art. 1Moderní jazykové modely jsou schopné generovat gramaticky správný, přirozený ja- zyk. Stále však mají potíže s commonsense reasoningem, což je úkol zahrnující vyvozování závěrů o běžných každodenních situacích bez explicitně uvedených informací. Předchozí výzkum tohoto tématu ukázal, že poskytnutí dodatečných informací z externích zdrojů pomáhá jazykovým modelům generovat lepší výstupy. V této práci zkoumáme metody získávání informací ze znalostních grafů a jejich využití jako dodatečného vstupu pro předem natrénovaný generativní jazykový model. Děláme to buď extrakcí podgrafu rele- vantního pro kontext, nebo pomocí grafových neuronových sítí, které předpovídají, které informace jsou relevantní. Kromě toho experimentujeme s post-editačním přístupem a s modelem natrénovaným ve víceúlohovém setupu (generování a klasifikace konzistence). Naše metody jsou hodnoceny na benchmarku CommonGen pro generativní common- sense reasoning s využitím automatických metrik i podrobné analýzy chyb na malém vzorku výstupů. Ukazujeme, že metody se zlepšují ve srovnání s jednoduchým přístu- pem spočívajícím ve vyladění jazykového modelu, ačkoli nepřekonávají nejlepší současné modely. 1Institute of Formal and Applied LinguisticsÚstav formální a aplikované lingvistikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult
Advances and Applications of DSmT for Information Fusion. Collected Works, Volume 5
This fifth volume on Advances and Applications of DSmT for Information Fusion collects theoretical and applied contributions of researchers working in different fields of applications and in mathematics, and is available in open-access. The collected contributions of this volume have either been published or presented after disseminating the fourth volume in 2015 in international conferences, seminars, workshops and journals, or they are new. The contributions of each part of this volume are chronologically ordered.
First Part of this book presents some theoretical advances on DSmT, dealing mainly with modified Proportional Conflict Redistribution Rules (PCR) of combination with degree of intersection, coarsening techniques, interval calculus for PCR thanks to set inversion via interval analysis (SIVIA), rough set classifiers, canonical decomposition of dichotomous belief functions, fast PCR fusion, fast inter-criteria analysis with PCR, and improved PCR5 and PCR6 rules preserving the (quasi-)neutrality of (quasi-)vacuous belief assignment in the fusion of sources of evidence with their Matlab codes.
Because more applications of DSmT have emerged in the past years since the apparition of the fourth book of DSmT in 2015, the second part of this volume is about selected applications of DSmT mainly in building change detection, object recognition, quality of data association in tracking, perception in robotics, risk assessment for torrent protection and multi-criteria decision-making, multi-modal image fusion, coarsening techniques, recommender system, levee characterization and assessment, human heading perception, trust assessment, robotics, biometrics, failure detection, GPS systems, inter-criteria analysis, group decision, human activity recognition, storm prediction, data association for autonomous vehicles, identification of maritime vessels, fusion of support vector machines (SVM), Silx-Furtif RUST code library for information fusion including PCR rules, and network for ship classification.
Finally, the third part presents interesting contributions related to belief functions in general published or presented along the years since 2015. These contributions are related with decision-making under uncertainty, belief approximations, probability transformations, new distances between belief functions, non-classical multi-criteria decision-making problems with belief functions, generalization of Bayes theorem, image processing, data association, entropy and cross-entropy measures, fuzzy evidence numbers, negator of belief mass, human activity recognition, information fusion for breast cancer therapy, imbalanced data classification, and hybrid techniques mixing deep learning with belief functions as well
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