Math Quiz: NYT Learning Network

Through Math for America, I am part of an on-going collaboration with the New York Times Learning Network.  My latest contribution, a Test Yourself quiz-question, can be found here:

https://learning.blogs.nytimes.com/2012/09/12/test-yourself-sept-12-2012/

This question has to do with the disproportionate number of 5-star ratings found on online review sites like Amazon.com.  How does this affect the overall average product rating?