How to calculate the overall rating of the review?

Hello, could you tell me how to calculate the overall rating for reviews of no more than 5 points?
For example there is a product iPhone 8, which has 3 of the criteria: Price, Quality.
First opinion: Price = 4, Quality = 5
Second opinion: Price = 1, Quality = 2
Third opinion: Price = 5, Quality = 5
In the database to record the item and record the total amount of criteria and the number of reviews, for example:
review_count = 3
rating_summ = 22

It is necessary to calculate the total amount of rating review_count and rating_summ not exceeding 5 score
June 7th 19 at 14:48
1 answer
June 7th 19 at 14:50
Well, if the criteria have equal weights, then calculate the average arifmeticheskoe all the criteria. If the criteria have weight — calculate a weighted average. And then arifmeticheskoe secondary all secondary arifmeticheskikh.

I understand that you have equal weight. Provided that in every opinion put down all the criteria, it all comes down to a simple formula:
Thank you very much, it seems to work, check with different versions of the review if be rules, the question is closed - nikita.Stracke commented on June 7th 19 at 14:53

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