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.
A great subject matter with a lot of interesting facts about sleep deprivation. I found parts a little far fetched and overuse of literary licence, but then why let probabilities get in the way of a good story. Read it while on holiday in Bali an easy read. Anne