Performance Analysis
What Really Matters with Machine Learning
History will look back on our time as the beginning of the artificial intelligence revolution. In 2017, artificial intelligences are beating us at Go, translating and inventing their own languages, helping us decide what to buy, writing for us, and composing music. Neural networks can even be used for image compression! As you might expect, the endpoint security industry is benefiting greatly from AI as we are using it for everything, from detecting threats to unusual network activity. However, sometimes the problem with a complex, new technology, apart from actually inventing and building it, is figuring out how to explain it to customers -- how does it work and why is it valuable.
Using Confusion Matrices to Quantify the Cost of Being Wrong
There are so many confusing and sometimes even counter-intuitive concepts in statistics. I mean, come on…even explaining the differences between Null Hypothesis and Alternative Hypothesis can be an ordeal. All I want to do is to understand and quantify the cost of my analytical models being wrong. For example, let's say that I'm a shepherd who has bad eyesight and have a hard time distinguishing between a wolf and a sheep dog. That's obviously a bad trait, because the costs of being wrong are very expensive: Okay, so I'm not a very good shepherd, but I am a very sophisticated shepherd and I've build a Neural Network application to distinguish a sheep dog from a wolf.
Cost-Sensitive Learning for Predictive Maintenance
Spiegel, Stephan, Mueller, Fabian, Weismann, Dorothea, Bird, John
In predictive maintenance, model performance is usually assessed by means of precision, recall, and F1-score. However, employing the model with best performance, e.g. highest F1-score, does not necessarily result in minimum maintenance cost, but can instead lead to additional expenses. Thus, we propose to perform model selection based on the economic costs associated with the particular maintenance application. We show that cost-sensitive learning for predictive maintenance can result in significant cost reduction and fault tolerant policies, since it allows to incorporate various business constraints and requirements.
Active Fairness in Algorithmic Decision Making
Noriega-Campero, Alejandro, Bakker, Michiel, Garcia-Bulle, Bernardo, Pentland, Alex
Society increasingly relies on machine learning models for automated decision making. Yet, efficiency gains from automation have come paired with concern for algorithmic discrimination that can systematize inequality. Substantial work in algorithmic fairness has surged, focusing on either post-processing trained models, constraining learning processes, or pre-processing training data. Recent work has proposed optimal post-processing methods that randomize classification decisions on a fraction of individuals in order to achieve fairness measures related to parity in errors and calibration. These methods, however, have raised concern due to the information inefficiency, intra-group unfairness, and Pareto sub-optimality they entail. The present work proposes an alternative active framework for fair classification, where, in deployment, a decision-maker adaptively acquires information according to the needs of different groups or individuals, towards balancing disparities in classification performance. We propose two such methods, where information collection is adapted to group- and individual-level needs respectively. We show on real-world datasets that these can achieve: 1) calibration and single error parity (e.g., equal opportunity); and 2) parity in both false positive and false negative rates (i.e., equal odds). Moreover, we show that, by leveraging their additional degree of freedom, active approaches can outperform randomization-based classifiers previously considered optimal, while also avoiding limitations such as intra-group unfairness.
Explainable Black-Box Attacks Against Model-based Authentication
Garcia, Washington, Choi, Joseph I., Adari, Suman K., Jha, Somesh, Butler, Kevin R. B.
Establishing unique identities for both humans and end systems has been an active research problem in the security community, giving rise to innovative machine learning-based authentication techniques. Although such techniques offer an automated method to establish identity, they have not been vetted against sophisticated attacks that target their core machine learning technique. This paper demonstrates that mimicking the unique signatures generated by host fingerprinting and biometric authentication systems is possible. We expose the ineffectiveness of underlying machine learning classification models by constructing a blind attack based around the query synthesis framework and utilizing Explainable-AI (XAI) techniques. We launch an attack in under 130 queries on a state-of-the-art face authentication system, and under 100 queries on a host authentication system. We examine how these attacks can be defended against and explore their limitations. XAI provides an effective means for adversaries to infer decision boundaries and provides a new way forward in constructing attacks against systems using machine learning models for authentication.
Comment on "DNA damage is a pervasive cause of sequencing errors, directly confounding variant identification"
Even if the 8-oxo-G artifacts are twice the context-specific background level (i.e., GIVG_T 2), this corresponds to only a 5 to 10% increase in the overall base-level error rate (summed over all sequence contexts; Figure 1, A to C), which is less than the intersample variability of error rates at a fixed oxoQ. A 5% increase in the base-level error rate results in a minor, if any, increase in false-positive mutation calls (Figure 1, E and F), because calling algorithms are designed to handle typical levels of sequencing error. Only at GIVG_T 5 (equivalent to oxoQ 35) do the additional errors from 8-oxo-G become comparable to the sum of all other errors and have an adverse impact on variant calling. The vast majority of samples in TCGA exhibit only minor 8-oxo-G damage that has minimal impact on mutation calling. Consequently, the claim that 73% of TCGA sequencing runs have extensive damage is misleading.
Unfolding Naive Bayes From Scratch
I have tried to keep things simple and in plain-English. The sole purpose is to deeply and clearly understand the working of a well know Text Classification ML Algorithm (Naïve Bayes) without being trapped in the gibberish mathematical jargon that is often used in the explanation of ML Algorithms which obviously lands you nowhere except for being relying on ML API's with almost zero understanding of how the things actually work! A complete clear picture of the Naïve Bayes ML Algorithm with all its mysterious mathematics demystified plus a concrete step taken forward in your ML voyage! The Grand Grand Grand Milestone # 3: The Testing Phase --Where Prediction Comes into the Play! Naive Bayes is one of the most common ML algorithms that is often used for the purpose of text classification.
Queue-based Resampling for Online Class Imbalance Learning
Malialis, Kleanthis, Panayiotou, Christos, Polycarpou, Marios M.
Online class imbalance learning constitutes a new problem and an emerging research topic that focusses on the challenges of online learning under class imbalance and concept drift. Class imbalance deals with data streams that have very skewed distributions while concept drift deals with changes in the class imbalance status. Little work exists that addresses these challenges and in this paper we introduce queue-based resampling, a novel algorithm that successfully addresses the co-existence of class imbalance and concept drift. The central idea of the proposed resampling algorithm is to selectively include in the training set a subset of the examples that appeared in the past. Results on two popular benchmark datasets demonstrate the effectiveness of queue-based resampling over state-of-the-art methods in terms of learning speed and quality.
Counterfactual Fairness in Text Classification through Robustness
Garg, Sahaj, Perot, Vincent, Limtiaco, Nicole, Taly, Ankur, Chi, Ed H., Beutel, Alex
In this paper, we study counterfactual fairness in text classification, which asks the question: How would the prediction change if the sensitive attribute discussed in the example were something else? We offer a heuristic for measuring this particular form of fairness in text classifiers by substituting individual tokens pertaining to attributes (e.g. sexual orientation, race, and religion), and describe the relationship with other notions, including individual and group fairness. Further, we offer methods, including hard ablation, blindness, and counterfactual logit pairing, for optimizing this counterfactual fairness metric during model training, bridging the robustness literature and the fairness literature. Empirically, counterfactual logit pairing performs as well as hard ablation and blindness to sensitive tokens, but generalizes better to unseen tokens. Interestingly, we find that in practice, the methods do not significantly harm classifier performance, and have varying tradeoffs with group fairness. These approaches, both for measurement and optimization, provide a new path forward for addressing counterfactual fairness issues.
Sample Efficient Adaptive Text-to-Speech
Chen, Yutian, Assael, Yannis, Shillingford, Brendan, Budden, David, Reed, Scott, Zen, Heiga, Wang, Quan, Cobo, Luis C., Trask, Andrew, Laurie, Ben, Gulcehre, Caglar, Oord, Aäron van den, Vinyals, Oriol, de Freitas, Nando
We present a meta-learning approach for adaptive text-to-speech (TTS) with few data. During training, we learn a multi-speaker model using a shared conditional WaveNet core and independent learned embeddings for each speaker. The aim of training is not to produce a neural network with fixed weights, which is then deployed as a TTS system. Instead, the aim is to produce a network that requires few data at deployment time to rapidly adapt to new speakers. We introduce and benchmark three strategies: (i) learning the speaker embedding while keeping the WaveNet core fixed, (ii) fine-tuning the entire architecture with stochastic gradient descent, and (iii) predicting the speaker embedding with a trained neural network encoder. The experiments show that these approaches are successful at adapting the multi-speaker neural network to new speakers, obtaining state-of-the-art results in both sample naturalness and voice similarity with merely a few minutes of audio data from new speakers.