Verbal probabilities: Very likely to be somewhat more confusing than numbers

Area of Science:

• Decision Science
• Cognitive Psychology
• Risk Communication

Background:

• Verbal expressions of probability are interpreted inconsistently.
• Numerical guidelines are often ignored when communicating uncertainty.
• Effective communication of probabilistic information is crucial for decision-making.

Purpose of the Study:

• To evaluate methods for improving the interpretation of verbal probabilities.
• To compare the effectiveness of different formats for presenting numerical guidelines.
• To enhance the correspondence between intended and interpreted meanings of probabilistic language.

Main Methods:

• An online experiment with 924 participants tested four presentation formats for numerical guidelines.
• Formats included bracketing in text, pop-up tooltips, separate windows, and a control group.
• Participants' interpretations of verbal probabilities were compared against US Intelligence Community Directive (ICD) 203 standards.

Main Results:

• Bracketing numerical guidelines within text substantially improved correspondence with intended meanings (66% vs. 32% in control).
• Other formats (tooltips, separate windows) did not significantly improve interpretation consistency.
• Evidence-based lexicons were constructed from participant judgments of verbal probability terms.

Conclusions:

• Presenting numerical probability guidelines directly within text is the most effective method for improving clarity.
• Aligning the intended and interpreted meanings of probabilistic terms reduces communication errors.
• Improved communication of uncertainty can lead to better decision-making under risk.