To complete the dice roll model, a probability is assigned to each outcome in the outcome space.
Each outcome receives a non-negative number, and the total probability across all outcomes is equal to 1. These probabilities are part of the model definition and must be specified explicitly.
In many introductory settings, all outcomes are assigned the same probability, producing a symmetric or “fair” model. This symmetry, however, is an assumption rather than a requirement. Unequal probabilities lead to a different, but equally valid, dice roll model.
The probability assignment determines how likely each outcome is, independently of how the outcomes are labeled.