Comparison tools provide a basis for making choices among competing alternatives. If you’ve ever shopped for a car, for example, you might have consulted a Web site such as Cars.com, which allows you to compare different kinds of automobiles on criteria such as fuel economy, safety features, and resale value (among many other criteria) and view reviews of each model. A growing number of Web sites, as well as apps that you can use on a tablet or smartphone, allow you to compare a number of products, including automobiles, cameras, and phones.

The creators of comparison tools usually try to provide both factual information, such as size and weight, and assessments of quality, such as rankings and ratings. Their goal is to provide readers with both objective data and qualitative judgments about the effectiveness, performance, or value of the items that are being compared. Users of comparison tools expect them to be easy to use. They also look for evidence that the creators of the tool have compiled information that can be trusted. More often than not, a person using one of these tools will value clarity and depth of information over appealing design.