Does the public understand evidence summaries with numbers?

Cameron Brick
Mar 25, 2020 · 3 min read

By Cameron Brick, Michelle McDowell, & Alexandra Freeman

It’s hard to communicate numbers to a broad public, as those trying to communicate in the current COVID-19 pandemic know all too well. A new study we’ve just carried out provides the best evidence yet that tables are better understood than text for understanding and comparing numbers.

Whether individuals are making personal medical decisions or deciding on policies for large groups, choosing between options requires high-quality evidence summaries about harms and benefits. Writing these summaries is difficult because it’s not clear how much information to include or how to present it. Previous research has compared many formats including tables, figures, and infographics. One promising format is a simplified table called a ‘fact box’.

We tested whether a simple table — a ‘fact box’ — might be better understood than plain text. What’s new about this study is that the text has exactly the same information as the table and was written to be very clear and accessible just as it is on, say, the NHS Choices website. We studied a large group of people (2,305) representative of the UK population, and found that putting information in the ‘fact boxes’ still helped people understand and remember much more than this simple text.

Figure 1. The fact box for the vaccine condition.

The results were strong: individuals who saw either fact box performed higher on a comprehension test than those who saw a passage of text with the same information.

Figure 2. Fact boxes were understood better than text-alone for both medical conditions (Flu = vaccine for influenza, and ear = antibiotics for ear infection). This rainbow plot was generated with ggplot in R.

The improvement held regardless of people’s ability with numbers or their education level. We also found that people spontaneously asked for more information about the quality and source of the information.

Figure 3. Fact boxes were better understood than text-alone for all levels of highest education.

We also tested how well people remembered the information after six weeks. Not very well — and that makes sense, since they didn’t see the information again before being tested! But fact boxes were still better understood after that delay, and when we showed them the same information again, fact boxes resulted in higher comprehension than the text.

Effective communication supports informed consent and decision-making and brings ethical and practical advantages. Fact boxes and other summary formats may be effective in a wide range of communication contexts.

For messages to support individual and policy decisions, they must be understood. If the central goal is something other than comprehension — for example persuasion or behavior change — this creates a lot of ethical questions. There are times in a risk communication crisis when messages should be designed for immediate public impact, for example during an evacuation order. But when making decisions that will affect oneself and others far into the future, it’s best to first make sure the message is understood.

In summary: the strongest scientific evidence to date suggests that tables are effective for communicating numbers to a broad public, including individuals who are less numerically capable. We need these tools for communicating all types of risk, including the current COVID-19 crisis.

Open-access PDF: Brick, C., McDowell, M., & Freeman, A. L. (2020). Risk communication in tables vs. text: a Registered Report randomised trial on ‘fact boxes’. Royal Society Open Science, 7, 190876. doi.org/10.1098/rsos.190876

Learn more

  • This open-access review is more zoomed-out It explain what makes communicating policy decisions difficult and how it’s currently done across many fields.
  • This preprint manuscript explores which icons are best understood to indicate effectiveness and evidence quality when comparing interventions.

Questions or comments: Dr Cameron Brick, cb954@cam.ac.uk, Winton Centre for Risk Communication

Dr Michelle McDowell, Harding Center for Risk Literacy

Dr Alexandra Freeman, Winton Centre for Risk Communication

The Winton Centre for Risk and Evidence Communication is…

Cameron Brick

Written by

Social psychologist www.cameronbrick.com Twitter: @CameronBrick

WintonCentre

The Winton Centre for Risk and Evidence Communication is hosted within the Department of Pure Mathematics and Mathematical Statistics in the University of Cambridge. Transparent evidence designed to inform, not to persuade.

Cameron Brick

Written by

Social psychologist www.cameronbrick.com Twitter: @CameronBrick

WintonCentre

The Winton Centre for Risk and Evidence Communication is hosted within the Department of Pure Mathematics and Mathematical Statistics in the University of Cambridge. Transparent evidence designed to inform, not to persuade.

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