Add baseline risk to every risk-reduction display
For risk-reduction comparison tasks, use baseline-risk annotation on quantitative risk displays to improve interpretation fidelity and mitigate inflated effect-size judgments for patient audiences.
- purpose:refine
- basis:empirical
- task:compare
- quality:fidelity
- lever:text-annotation
- communication:context
- component:annotation:use
- audience:general-public
advice
Baseline-risk annotation
Annotate every absolute or relative risk reduction with the starting risk. For example, place the baseline percentage or frequency next to the reduction figure instead of showing only the reduction claim.
reason
Why baseline risk changes interpretation
A reduction number means something different at different starting levels. Baseline risk gives readers the reference they need to judge whether a reported change is small or large.
Mechanism: Baseline context anchors the effect size, so readers interpret the reduction against the starting risk instead of overreacting to a standalone relative or absolute change.
Evidence: The review reports that adding baseline risk to either absolute or relative risk-reduction information strongly improves the accuracy of interpretation (Ancker & Kaufman, 2007).
context
Use when the display compares a before-versus-after risk
- User Goal: Interpret a treatment effect accurately.
- Task: Compare a baseline risk with a reduced risk.
- Data: Absolute risk reductions or relative risk reductions.
- Chart Setting: Numeric or graphical risk communication in patient-facing material.
- Audience: Patients or health consumers.
- Success Criterion: Accurate interpretation of the size of the reported effect.
exceptions
Do not use outside risk-reduction communication
Break it when: The display is not communicating a risk-reduction comparison. Why: The reported benefit is specific to interpreting risk reduction information.
costs
Tradeoff of adding baseline risk
Sacrifice: You give up a standalone reduction headline. Risk: If baseline risk is omitted, relative differences can look larger than the underlying change. Mitigation: Put the starting risk in the same label or sentence as the reduction.
mistakes
Common failure with effect-size displays
Mistake: Showing only the absolute or relative reduction value. Why it fails: Readers cannot judge the size of the effect in context and may overread the claim.
check
Check for missing baseline risk
Failure Sign: The display states a reduction but does not show the starting risk. Quick Check: Ask a reviewer to point to the baseline risk directly on the display. Stronger Test: Show the same effect with and without baseline risk and check whether reviewers give the same interpretation only after the baseline is added.
fix
Fix the effect-size display
- Add the baseline percentage or frequency next to the reduction value.
- Pair a relative reduction with both the starting risk and the ending risk.
- Pair an absolute reduction with the starting risk instead of leaving the reduction standalone.