Words to Probability

What does likely mean? How about rarely, almost certainly, or a real possibility?

Although these words feel precise, people often assign them very different meanings. This can cause confusion when it comes to decision-making.

This simple activity helps you experience that ambiguity firsthand and discover why expressing uncertainty with numbers can lead to clearer communication and better decisions. The activity was popularized by Alliance Advisory Council Member Michael Mauboussin, who has long used it to illustrate how differently people interpret probability language.

When people compare their estimates, they’re often surprised by how much variation exists, even among teammates or peers interpreting the exact same words. The discussion that follows provides a natural introduction to thinking probabilistically and highlights the importance of communicating uncertainty with greater precision.

This activity works well as:

• A warm-up for classrooms lessons on probability, forecasting, or uncertainty
• An introduction to thinking probabilistically
• A discussion starter about communication and decision-making
• A professional learning activity for educators or teams

This downloadable resource includes:

• An individual probability estimation worksheet
• A group comparison activity
• Reflection questions to guide classroom discussion

• Grades 6–12
• Post-secondary classrooms
• Professional learning
• Team meetings and workshops

This resource helps learners strengthen their understanding of:

• Thinking Probabilistically
• Navigating uncertainty
• Forecasting
• Calibration