1A-1 DO RISK VISUALIZATIONS IMPROVE THE UNDERSTANDING OF NUMERICAL RISKS? A RANDOMIZED, INVESTIGATOR-BLINDED GENERAL POPULATION SURVEY

Monday, October 24, 2016: 2:00 PM
Bayshore Ballroom Salon D, Lobby Level (Westin Bayshore Vancouver)

Jonathan R.G. Etnel1, Thomas H. Oostdijk2, Yvonne J.M. Licher2, Sanne Treep2, Peterke J. van der Zwaag2, Ad J.J.C. Bogers, MD, PhD1 and Johanna Takkenberg, MD, PhD1, (1)Department of Cardiothoracic Surgery, Erasmus University Medical Center, Rotterdam, Netherlands, (2)Faculties of Industrial Design, Physics and Mathematics, Delft University of Technology, Delft, Netherlands
Purpose: Information portals and decision aids often employ risk visualizations to help users better understand numerical risks. But are they indeed more effective than simple numerical risks alone? We assessed numeracy among the general Dutch population and investigated the effectiveness of various risk visualizations in improving the understanding of numerical risks.

Method: Randomly sampled from four public locations across the Netherlands and based on our power calculations, 187 members of the general Dutch population were included. Each respondent completed a questionnaire (4 questions) on basic risk conversions from percentages to natural frequencies(2 questions) and vice versa(2 questions), adapted from the Numeracy Scale. In each of these four questions, the numerical risk was portrayed by a different visualization: a pie chart, icon array or bar graph. Question–visualization combinations were varied across four different versions of the questionnaire. A fifth version of the questionnaire contained no risk visualizations. Allocation of the respondents to one of these five versions of the questionnaire was randomized and investigator-blinded. Respondent performance was scored ordinally from 0-4 corresponding with the number of questions answered correctly. Demographics and individual visualization preference were also recorded.

Result: Age(p=0.075), gender(p=0.849) and education level(p=0.069) were all comparable to the overall general Dutch population. Only 73 respondents(39.0%) answered all four questions correctly and 41(21.9%) answered three out of four questions correctly. Younger age(odds ratio[OR]/10 years of age=1.19;p=0.015) and higher education level(OR=1.27;p<0.001) were independently associated with a higher score, whereas male vs. female gender was not(OR 1.26;p=0.399). The use of risk visualizations was not associated with a higher score(OR=1.05;p=0.878). This finding held when considering each question individually(n=748 [4 per respondent];66.7% correctly answered): questions supported by a visualization were not more frequently answered correctly than questions that were not (OR=1.07;p=0.700). Each visualization considered separately, neither pie charts(OR=1.34;p=0.236), icon arrays(OR=1.12;p=0.590) nor bar graphs(OR=0.81;p=0.381) significantly improved the odds of answering a question correctly compared to no visualization. Pie charts were significantly more effective than bar graphs(p=0.031). Individual preference for a certain visualization was not associated with its effectiveness(OR=1.02;p=0.905).

Conclusion: The understanding of numerical risks among the general Dutch population is poor and is not improved by the use of risk visualizations. Pie charts are more effective than bar graphs in conveying risks. This provides helpful information for the development of patient information portals and decision aids.

See more of: ORAL ABSTRACTS: RISK PERCEPTION AND RISK COMMUNICATION

See more of: 38th Annual North American Meeting of the Society for Medical Decision Making