The phrase "to do a comparison" means to examine two or more things, people, or ideas in order to see how they are different or similar. Full definition
As a shopper, you have the option of doing comparison shopping where you look at quality, ease of use, and price of competing products. (babyseats.reviews)
However, the researchers tried to minimize this bias by doing comparisons of similar - intensity studies. (alivebynature.com)
You can easily do a comparison between one free dating web site and the other. (articlesfactory.com)