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arXiv · 2402.09702

Sparse and Faithful Explanations Without Sparse Models

Yiyang Sun·Zhi Chen·Vittorio Orlandi·Tong Wang·Cynthia Rudin
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Abstract

Even if a model is not globally sparse, it is possible for decisions made from that model to be accurately and faithfully described by a small number of features. For instance, an application for a large loan might be denied to someone because they have no credit history, which overwhelms any evidence towards their creditworthiness. In this work, we introduce the Sparse Explanation Value (SEV), a new way of measuring sparsity in machine learning models. In the loan denial example above, the SEV is 1 because only one factor is needed to explain why the loan was denied. SEV is a measure of decision sparsity rather than overall model sparsity, and we are able to show that many machine learning models -- even if they are not sparse -- actually have low decision sparsity, as measured by SEV. SEV is defined using movements over a hypercube, allowing SEV to be defined consistently over various model classes, with movement restrictions reflecting real-world constraints. We proposed the algorithms that reduce SEV without sacrificing accuracy, providing sparse and completely faithful explanations, even without globally sparse models.

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Yiyang Sun, Zhi Chen, Vittorio Orlandi, Tong Wang, Cynthia Rudin. 2024-03-09. Sparse and Faithful Explanations Without Sparse Models. https://arxiv.org/abs/2402.09702

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