Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
I installed this left in my garage two weeks ago. I wish that had done it five years ago. Easy to install, just follow the instructions supplied. No more carrying things up the stairs. Gone with the push of a button.