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.
Really straight forward book. I followed this step by step and we had great success. I highly recommend to anyone looking at potty training in a quick and efficient way. I read other books and this one I found to be the best.