In Chapter 1 it was stated that the field of statistics is concerned with the acquisition, summarization, analysis, and interpretation of numerical data obtained using sampling. In the analysis and interpretation phases of the statistical process, estimates are made. When this is done, there must be some measure of the likelihood that the estimate is adequate. As a consequence, the concepts of probability permeate the entire structure of statistics, making it imperative that workers in the field have at least some knowledge of, and appreciation for, probability.