This week in my UX studies, we began to focus more intently on the different types of studies with emphasis on what works best when. This is really important to understand as a future usability expert because you will not always be engage into a project from the beginning.
In some cases you will be brought in at the design phase, meaning you will be able to come up with multiple designs and prototypes and really be able to perform good formative studies, meaning you are learning from them to get to the final solutions.
In other cases, everything is "done" and your being brought it to determine places where things are broken. In this case, your more likely to be doing a summative study or evaluation of a product that already exist to find holes and areas for improvement, however, the is less likelihood you will change directions completely. Instead, you will likely being just patching up areas for improvement.