You are expected to find a project that interests your group with the help of the TAs and your instructor. Since the project is the majority of your grade, you are expected to find a project that is "significant". The following are some samples that help you decide what is meant by "significant".

Sample Project Proposals from Last Year

Please note that you don't have to follow your project proposal. The proposal is meant to help you start thinking about the project early in the course and make sure you stay on track. It is perfectly fine if you deviate from the original project proposal you submitted as long as the TAs and the instructor approve (and in some cases recommend) it. Here are sample project proposal from last year:

Sample Project Reports from Last Year
The following are some sample project reports from last year. Note that it is perfectly fine if your groupmate(s) decide to drop the course. Our expectations of the project will be according to the number of people in the group. Expectations from a group of four is higher than that of a group of two or one. You can see from these examples that some groups finished the course as a group of one or two. But they still managed to do a good job and get a high grade for their project.
Sample Projects from Stanford University

If you like to see more sample projects, please see the Stanford Machine Learning course projects from previous years 2017, and 2018.