I purchased this book as a supplement for my Graduate-level course. It covered much of the "Proof left as an exercise for the reader" material in the course text. I work with probability and statistics and I use this book as a back-up for when I forget or encounter a problem requiring knowledge of statistics more obscure than Mean, Median, and Mode. The author has abbreviated proofs for many formulae. The examples are clear and support the material. An Instructor's Solution Manual would be helpful for autodidacts like myself. This book is well worth the price. I recommend it for business people who need it for work and for graduate-level students in a course on probability and/or statistics.