algorithm used to calculate 5 star ratings
algorithm, rating-system, weighted-average
Solution
That's a weighted average, where you weigh each rating with the number of votes it got:
(5*252 + 4*124 + 3*40 + 2*29 + 1*33) / (252+124+40+29+33) = 4.11 and change
Problem
I need to calculate 5-star ratings like the one on Amazon website. I have done enough search to find what is the best algorithm, but I am not able to get a proper answer. For example, if these are the ratings ``` 5 star - 252 4 star - 124 3 star - 40 2 star - 29 1 star - 33 ``` totally 478 reviews Amazon has calculated this to be "4.1 out of 5 stars". Can anyone tell me how this figure is arrived at? I am not able to get this just by doing average.