Visual displays can help patients to understand medical information, but may not be as useful to patients with low graph literacy. These patients may not have enough knowledge about the properties of different kinds of displays and procedures for interpreting them. However existing measures of graph literacy are either too difficult or too long for everyday medical research and practice. Here we describe a short test of graph literacy that fills this gap.
Method:
The study consisted of two phases. In the first phase, 51 participants in a laboratory setting completed 13 items included in a longer graph literacy scale developed by Galesic & Garcia-Retamero (2011), as well as 16 items involving complex visual displays. All items had health-related content. The complex displays included spatial features, such as height of bars, that were incongruent with the information conveyed by conventional features, such as titles, labels, and scales. Based on the results of the first phase, we selected 4 of the initial 13 items for the short graph literacy scale. In the second phase, we used these 4 items to predict accuracy of understanding of different types of graphs in a study conducted on nationally representative samples of people 25 to 69 years of age in Germany (n= 495) and the United States (n= 492).
Result:
In the first phase in the laboratory, we analyzed correlations of each of the 13 original graph literacy scale items with the total score on the 16 complex displays, and selected 4 items that correlated with the total score most highly and predicted it independently of numeracy skills. Each of these items included a different type of display: bar, line, pie chart, and icon array. In the second phase on the nationally representative samples, we found that these 4 items were as successful as the longer 13-item scale in predicting accuracy of understanding of different types of graphs displaying medical information.
Conclusion:
The new 4-item scale is fast and psychometrically valid method for measuring graph literacy. The scale can be used in both medical research and practice to test whether different visual displays can be understood by patients with low graph literacy skills.