Probability can be interpreted in different ways, and these interpretations shape how you approach statistical inference. The frequentist view sees probability as the long-run frequency of an event occurring in repeated, identical trials. For example, the probability of a coin landing heads is the proportion of heads observed after many flips. In contrast, the Bayesian perspective treats probability as a degree of belief—a subjective measure reflecting your uncertainty about a proposition, given your current knowledge. This means probability is not just about long-run frequencies but about how strongly you believe in a particular outcome based on available information.

The subjective probability approach, foundational to Bayesian statistics, acknowledges that different people may assign different probabilities to the same event, depending on their prior knowledge and experience. This interpretation is rooted in philosophical debates about the nature of probability: is it an inherent property of the world, or does it represent personal uncertainty? Bayesian reasoning embraces the latter, allowing you to update your beliefs as new evidence arrives. In practice, this means that Bayesian inference is inherently personal and dynamic, whereas frequentist inference relies on objective, repeatable experiments.