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.
Another great book by author Bill O'Neill. He has a great way of grouping facts and trivia in an interesting and entertaining way. Great resource for setting Quiz Questions and a great resource for those that go to quiz nights.