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.
Bought it mainly for fruit or vegetable smoothies, and it does a sensational job. Easy to prepare smoothies, easier still to clean afterwards. One downer though, in the fine print it mentions that the cutting head should be replaced every six months. These can be very expensive depending on where you buy them. In the interests of full disclosure, this fact should be mentioned in ore-purchase advertising.