What type of probability is defined by the nature of certain events?

A priori probability is based on theoretical principles and logical analysis rather than on empirical evidence or experimentation. It is defined by the inherent nature of certain events, often derived from established rules or models. This type of probability relies on the understanding of potential outcomes based on what is known, independent of any observation or experience.

For example, when flipping a fair coin, the a priori probability of landing heads is 0.5, based purely on the understanding that there are two equally likely outcomes. This is a logical deduction derived from the nature of the event (the coin flip), rather than from previous experimental data or observations.

In contrast, other types of probability, such as empirical probability, rely on actual experience or experiments to determine the likelihood of events, while subjective probability is influenced by personal judgment or belief. Thus, a priori probability stands out because it is defined through theoretical foundations rather than practical evidence.