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When you shop online, there’s almost no limit to what you can buy, and consumers can shop ‘til they drop without even changing out of their pajamas. But with so many things available for purchase, how can we separate the good products from the bad?

In this lesson, students look at different ways to summarize online product ratings. From averages to ratios, they discuss which approaches are the most trustworthy, and what retailers can to do ensure that their ratings match the actual quality of their products.

Students will

  • Summarize the distribution of product ratings using different methods, including the mean and the mode
  • Discuss which methods of summarizing ratings are the most/least trustworthy
  • Understand that the average rating stabilizes as the number of reviews grows, and that average ratings of products with a small number of reviews are less trustworthy
  • Discuss what a website can do to ensure that its reviews are helpful

Before you begin

Students should have experience adding and subtracting integers, and should be able to calculate simple ratios. The most complicated mathematical questions involve averaging, and prior experience calculating averages is assumed.

Common Core Standards

Content Standards
Mathematical Practices

Shoutouts, NPR's Planet Money