From the Analytics tab you can access several data sources on your customer voice:
On the top of the dashboard, a chart details the different review ratings that your products have received across time. This chart is highly customizable. You will be able to select different time frames and time aggregations (daily, weekly, and monthly). It is also possible to apply product ASIN, tag, brand, category, and marketplace filters to refine the chart's data.
In the bottom half of the Analytics dashboard, you can access a table that outlines each one of your ASIN with a count of your reviews, question, and an average star rating. Remember to select a longer time frame to visualize a more comprehensive summary.
For complete guide, visit The Complete Guide to Reviews & Questions.