Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
The book is fairly high in price but well worth it. The book is full of full-color pictures and graphs. Tons of good, valuable information in an easy to understand format. This will be my reference at my desk from now on. Outstanding book.