Use icon arrays that show natural frequencies for low-numeracy risk communication
For probability communication in health decisions, use natural-frequency encoding on risk displays to improve fidelity and mitigate low-numeracy and denominator-neglect errors for readers with low graph or health literacy.
- purpose:refine
- basis:empirical
- operator:uncertainty
- quality:fidelity:use
- lever:encoding
- knowledge:low
- literacy:novice
advice
Natural-frequency encoding
Use icon arrays that depict probability as counts out of a fixed total when readers may struggle with percentages. For example, show affected cases as filled icons out of 100 for treatment and no-treatment conditions, so readers can compare risk by perception instead of calculation.
reason
Why icon arrays help low-numeracy readers
Percentages and probabilities are hard for many readers to reason about. An icon array turns the same information into natural frequencies and lets readers compare visible counts rather than compute ratios.
Mechanism: The display converts abstract probability into countable cases and supports perceptual comparison instead of arithmetic.
Evidence: The review reports that visual depictions of health risk, especially icon-array-style natural frequencies, are particularly helpful for people with lower health literacy, graph literacy, and numeracy (Padilla et al., 2018).
context
Use when risk probabilities must be understood
- User Goal: Make or support a treatment or risk decision.
- Task: Compare probabilities across alternatives.
- Data: Probability or risk information that can be expressed as counts out of a common denominator.
- Chart Setting: Health risk displays where percentages or probabilities might otherwise be shown alone.
- Audience: Readers with low numeracy, low graph literacy, or low health literacy.
- Success Criterion: Accurate understanding of relative risk without heavy calculation.
exceptions
Do not use when the message is not probabilistic risk
Break it when: The decision does not depend on comparing probabilities or risk levels. Why: The benefit comes from converting probability into natural frequencies that can be compared visually.
costs
Costs of icon-array encoding
Sacrifice: The display is less compact than a short numeric statement. Risk: The visual count can dominate the presentation even when the audience only needs a precise probability notation.
mistakes
Common risk-communication failure
Mistake: Present only percentages or probabilities to readers who must compare risks but may have low numeracy. Why it fails: The display forces mathematical interpretation where a perceptual comparison would work better.
check
How to test whether the risk display is doing its job
Failure Sign: Readers start calculating ratios, confuse denominators, or misstate which option is riskier. Quick Check: Ask whether the comparison can be answered by counting visible cases rather than computing percentages. Stronger Test: Compare the icon-array version against a percentage-only version on a simple risk-choice question.
fix
How to convert the display
- Convert each probability to a visible count out of the same denominator.
- Draw one icon per case and fill only the affected cases.
- Keep the compared options on matched totals so the reader can compare counts directly.
- Remove wording that forces readers back into percentage calculation when the visual count already answers the question.