Impact on Average Rating
The impact lets you know how the overall average rating of your product was affected by the specific review. Larger negative impacts require your immediate attention.
(Image: -0.50 = Impact, 4.0 = new rating, (3) = new total number of reviews)
Before the new review came in:
Four existing 5-star reviews => 4x5 : 4 = 5 => the rating is at 5
After the new 4 star review comes in.:
The calculation becomes (4x5 + 1x4) : 5 = 4,8 => the rating is now at 4,8
The impact of that review is the difference between 5 and 4,8 => -0,2