Amazon calculates a product’s star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
The three Federation books are an excellent read. Must admit though that I was a little disappointed in the Hidden Federation. I was expecting more that just a reporter checking on how earth was getting on in belonging to the Federation. Saved somewhat in the end with getting rid of the US president and allowing the American population to make the decision on whether to join or not.