Similar to whether a question is answerable, by “appropriately scoped” we are more specifically targetting scale.
For instance, if you are relatively new to CSEd research, targetting a project that takes one semester to do is probably a good idea. Smaller successess will lead to larger ones! Don’t be afraid to take smaller steps first!
Do you have in your mind that you’ll interview 300 students as a part of data gathering? Perhaps you should scale that back early on. Do you have help with data processing? What will your teaching load be like during the project?
Take all of these external factors into consideration to help you narrow your question even further into something you know you can complete!