Who proficts from visual aids: Overcoming challenges in people's understanding of risks
Section snippets
Introduction and background
Increased emphasis on patient-centered decision making has shifted responsibility to patients, who now more than ever need to understand numerical information to actively participate in making decisions about their health (Barry, 1999, Hanson, 2008). Informed consent laws, for instance, mandate that patients must be informed about risks before any treatment can be implemented (Garcia-Retamero & Galesic, 2009b). Understanding a treatment risk reduction implies taking into account the number of
Sample
The study was conducted on probabilistic national samples in the United States (n = 492) and Germany (n = 495) in July and August of 2008, using panels of households selected through probabilistic random digit dial telephone surveys and supplied with equipment that enabled them to complete computerized questionnaires. The panels, built and maintained by the companies Forsa (Germany; 20,000 households, 11% of those in the initial sample) and Knowledge Networks (43,000 households, 16% of those in
Results
To assess the effect of numerical format and visual aids, and their interaction with numeracy, graph literacy, and country on estimates of treatment risk reduction, we conducted mixed analyses of variance (ANOVAs), following Lunney (1970) and Cleary and Angel (1984). Tukey's HSD (honest significant difference) test was used for post hoc analyses.
Which visual aids lead to the most accurate perceptions of risk reduction? Does depicting the overall population at risk improve accuracy? When
Discussion and conclusions
Building on previous research showing that problems with understanding numerical information often reside not in people's minds but in the representation of the problem (Gigerenzer and Hoffrage, 1995, Gigerenzer et al., 2008), our results show that visual aids help to modify incorrect expectations about treatment risk reduction and have important implications for medical practice.
First, our findings showed large improvements in accuracy when either icon arrays or bar graphs were added to
Acknowledgements
We thank those who participated in the survey or provided feedback about the design of the study and data analyses. We also thank Anita Todd for editing the manuscript. This study is part of two projects, “Helping people with low numeracy to understand medical information,” funded by the Foundation for Informed Medical Decision Making (U.S.) and the Max Planck Society (Germany), and “How to improve understanding of risks about health (PSI2008-02019),” funded by the Ministerio de Educación y
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