Society Of Actuaries – Probability (SOA Exam P) Practice Exam

The area under a probability density function (PDF) curve is a fundamental concept in probability theory. Specifically, this area represents the total probability of the outcomes described by the distribution. Since a probability distribution must account for all possible outcomes, the area under the curve must equal 1. This reflects that the sum of probabilities for all possible outcomes in a continuous distribution is one, ensuring that the total probability is conserved and correctly normalized. In mathematical terms, for a continuous random variable defined by a probability density function, the integral of the PDF over its entire range produces a value of 1, indicating certainty that some outcome will occur. Thus, stating that the area under a probability density function curve equals 1 encapsulates the essence of probability distributions and aligns with the foundational principles of probability theory.