Quantitative meanings of verbal probability expressions

Area of Science:

• Cognitive psychology
• Linguistics
• Decision science

Background:

• Verbal probability expressions are widely used but lack precise quantitative meaning.
• Understanding these expressions is crucial for accurate risk communication and decision-making.

Purpose of the Study:

• To quantitatively define the meanings of 18 common verbal probability expressions.
• To investigate the consistency and relationships between these expressions.

Main Methods:

• Frequency distributions of best-representing numbers for each expression.
• Word-to-number acceptability functions defining numerical ranges.
• Number-to-word acceptability functions mapping numerical ranges to expressions.

Main Results:

• High agreement with existing research and consistency across methods.
• "Probable" and "likely" expressions were found to be quantitatively synonymous.
• Positive expressions (e.g., "likely") were closer to 50% meaning than negative counterparts (e.g., "unlikely"), except for "chance" expressions.

Conclusions:

• The study successfully derived fuzzy-set membership functions for probability words.
• The findings support ongoing efforts to codify probabilistic language for clearer communication.