A professor of psychology at Vassar College is the author of this impressive online statistics textbook. Seventeen chapters and numerous appendixes range in topic from beginning concepts to what would likely be covered in a second or intermediate course in statistics. Easy to navigate, the online interface provides quick access to all sections of the book, and some of the book's material is interactive, such as calculators and sampling distribution functions. A companion site to the text, offered by the same individual, has a large selection of statistical tools and demonstrations.