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.
I knew this was popular because I used to volunteer at a shelter that used these. My cat loves it, it's her favorite. I have added extra jingly balls to the track for even more fun! Definitely a good purchase!