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.
This is an excellent book for everyone. It gives tips for carrying that conversations with anyone and everyone that you tries to avoid for fear of a conflict. It gives various approaches and insight as to why you should hold that discussion instead of avoiding it.
Gives numerous examples and scenarios too. Must read!