All plays
When to use it
When the site has review or rating markup somewhere, but not on the product pages with the most visitors.
How to run it
Show the star average and review count next to the product title and price, and surface the first few reviews high on the page.
Why it works
Make it safe to believe you
The first five reviews do most of the work, so you don't need hundreds. Northwestern's Spiegel Research Center found purchase likelihood is 270% higher for a product displaying five reviews vs none.
Source: Spiegel Research Center (Northwestern)