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Epidemiology as a Framework for Large-Scale Mobile Application Accessibility Assessment

Mobile accessibility is often a property considered at the level of a single mobile application (app), but rarely on a larger scale of the entire app "ecosystem," such as all apps in an app store, their companies, developers, and user influences. We present a novel conceptual framework for the accessibility of mobile apps inspired by epidemiology. It considers apps within their ecosystems, over time, and at a population level. Under this metaphor, "inaccessibility" is a set of diseases that can be viewed through an epidemiological lens. Accordingly, our framework puts forth notions like risk and protective factors, prevalence, and health indicators found within a population of apps. This new framing offers terminology, motivation, and techniques to reframe how we approach and measure app accessibility. It establishes how app accessibility can benefit from multi-factor, longitudinal, and population-based analyses. Our epidemiology-inspired conceptual framework is the main contribution of this work, intended to provoke thought and inspire new work enhancing app accessibility at a systemic level. In a preliminary exercising of our framework, we perform an analysis of the prevalence of common determinants or accessibility barriers. We assess the health of a stratified sample of 100 popular Android apps using Google's Accessibility Scanner. We find that 100% of apps have at least one of nine accessibility errors and examine which errors are most common. A preliminary analysis of the frequency of co-occurrences of multiple errors in a single app is also presented. We find 72% of apps have five or six errors, suggesting an interaction among different errors or an underlying influence.