Do you think you can find the lowest prices by shopping online? Think again.

A new study by researchers at Northeastern University confirmed the extent to which major e-commerce websites show some users different prices and a different set of results, even for identical searches.

For instance, the study found, users logged in to Cheaptickets and Orbitz saw lower hotel prices than shoppers who were not registered with the sites. Home Depot shoppers on mobile devices saw higher prices than users browsing on desktops. Some searchers on Expedia and Hotels.com consistently received higher-priced options, a result of randomized testing by the websites. Shoppers at Sears, Walmart, Priceline, and others received results in a different order than control groups, a tactic known as “steering.”

Time