Evaluating a Tool for Improving Accessibility to Charts and Graphs

This article reports a case study of the iterative design and evaluation of a natural language-driven assistive technology, iGraph-Lite, providing people who are blind access to line graphs. Two laboratory-based usability studies involving blind and sighted people are presented with a discussion of the ensuing implementation of changes. Blind participants were found to adopt different graph interrogation strategies than sighted participants. A small field study is then reported in which a blind user who works with graphs took part to determine the degree to which the iGraph-Lite commands would meet the needs of blind graph experts. The final study invited sighted graph experts and novices to visually inspect and explain a set of line graphs comparable to those used in the usability studies. It aimed to highlight the concepts and the range of words sighted people use, to ascertain the appropriateness of the iGraph-Lite lexicon. A set of preliminary guidelines is presented.