The Frequentist Intuition behind Assigning Probabilities
An event is something that might or might not occur when some repeatable procedure is performed. A frequentist approach to probability entails assigning a probability to an event such that the relative frequency with which occurs approaches as the number of repetitions of the procedure grows.
In this Demonstration, the procedure is the tossing of three fair dice. You can choose from a few events and watch how the relative frequency of their occurrence (blue plot) fluctuates about the theoretical probability assigned to them (red line).