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.
So far I have used this book the most of the 3 Excel books I bought. It is easy to follow the instructions and have the results work. I was able to create column functions with little to no effort with this book.