In the area of statistical communications, a well-developed theory has grown to cover the testing for the presence of a desired process (signal) in the presence of an undesirable random process (noise). This book presents an adaptation of this theory. Originally published in 1965. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.