Undergraduate textbooks for statistics courses in the behavioral, biological, and social sciences must devote so much space to the nuts-and-bolts details of statistical methods that they have little left over for the larger conceptual framework of probability theory. This brief, lucid book fills the gap with its intelligible and in-depth explanation of probability, laid out step-by-step in a clear and congenial fashion. Even the student with little background in mathematics will find it readable and accessible.