The mastery bar reflects our confidence that you truly understood the learning objectives in an assignment, will retain the understanding, and are prepared to advance to the next topic. When your mastery bar reaches 100%, you are done with the assignment. Depending on how you answer the questions in the assignment, that might take more or less time than average, so don't worry if you have a longer experience!
As you answer questions, we incorporate the results into the full history of everything you've done in alta assignments, quizzes, and tests. We use this history to update the mastery bar, which is shown at the top of your screen. In addition to the assignment-level mastery bar, you also have access to a more fine-grained view by clicking the info icon to the right of the assignment’s mastery bar. This will take you to a "Your Mastery Breakdown" screen, which shows your mastery on each learning objective for the assignment.
The mastery bar represents our best estimate of your mastery, so it will move up and sometimes down. This means that if you get a question wrong, the mastery bar might go down, since we just learned more about how much you have currently mastered these topics. This is not a punishment. We don’t think of the mastery bar as “how much work you have left,” but instead “how much more you have to learn before mastering the topic.” Don’t worry, though - you can use the answer explanations to learn the material, and your mastery bar will go up as soon as you start answering questions correctly!