Accessibility for people with low vision of statistical graphics in the digital press: A methodological proposal based on heuristic indicators

Abstract

A new set of heuristic indicators is presented for the evaluation of the accessibility of statistical charts for people with impaired vision and color vision deficiency (CVD), as well as a methodology for their application. To validate the proposal, a heuristic evaluation of the accessibility of 35 charts published in 5 Spanish and 2 international newspapers is carried out. The results show that the proposed indicators enable the detection of a greater number of unique problems, present a better distribution of problems among heuristics, and enable the detection of more severe and specific problems compared with the Web content accessibility guidelines (WCAG). Regarding the problems detected, the lack of text alternatives to charts in bitmap format stands out, a problem that also occurs in the case of charts in SVG format, for which standards such as WAI-ARIA are not used for labeling the marks. The latter also underlines the poor use of indicators to highlight the elements that receive focus, or their inaccessibility through a keyboard interface. Other common problems with both types of charts are the non-text contrast ratio, which in many cases is below the minimum required, too small a font size, or the non-systematization of the use of color palettes appropriate for people with CVD. The comparison between national and international media reveals that, although higher scores are obtained by international media, they share a significant number of the problems identified for Spanish media. The list of principles obtained, beyond proving helpful for evaluative purposes, is also useful as a guide for creating accessible charts that could be easily incorporated into the style guides of the analyzed media.