A new scale for assessing perceptions of chance: a validation study.

Area of Science:

• Health risk perception
• Psychometrics
• Risk communication

Background:

• Assessing patient perception of health risk likelihoods is crucial but challenging, especially for low probabilities (<1%).
• Existing scales for measuring probability perception lack validation and struggle with low-probability events.

Purpose of the Study:

• To compare the validity and reliability of a novel visual analog scale with logarithmic "magnifying glass" feature against three benchmark scales.
• To evaluate the usability of the new scale for assessing probability perception.

Main Methods:

• A survey study involving 100 veterans/family members and 107 university faculty/students.
• Participants estimated probabilities of six events using a "magnifying glass" logarithmic scale and three benchmark scales (linear analog with words, linear analog with numbers, "1 in x").
• Scales were assessed for validity (ranking correlation), test-retest reliability (2-week interval), and usability (response errors, user feedback).

Main Results:

• The "magnifying glass" and linear scales outperformed the "1 in x" scale in validity, reliability, and usability.
• The "magnifying glass" scale demonstrated comparable validity (r=0.72) and reliability (r=0.55) to linear scales.
• The "magnifying glass" scale uniquely facilitated accurate estimation of low probabilities (e.g., <1%), unlike linear scales.

Conclusions:

• The "1 in x" scale is ineffective and difficult to use for probability perception.
• The "magnifying glass" scale offers a valid, reliable, and usable method for assessing health risk perception, particularly for low probabilities.
• This scale enhances the ability to capture nuanced low-probability judgments, improving risk communication.