To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyzes reviews to verify trustworthiness.
Material in the book was fine to read, but it did an awful job of walking you through the process of solving some of the example problems. Not very intuitive and wouldn't recommend it to other undergraduate students. Much better resources on the internet for much cheaper.