Why your mastery may change on Mondays

Every Monday, I recalibrate the mastery system using the latest available student response data. This means your mastery may move slightly up or down, even if you have not completed another paper.

Why is this necessary?

Your mastery is an estimate of your ability, based on your answers and the estimated difficulty of the questions you have attempted. Neither estimate is fixed forever.

As more students complete papers, we gain more evidence about how difficult each question is. The weekly recalibration uses this additional evidence to update both question difficulties and students' ability estimates together.

The aim is to make the estimates better informed as the amount of data grows.

What does this mean for my mastery?

The same answers can lead to a slightly different ability estimate when the system has a better understanding of the questions involved. For example, successfully answering a question that turns out to be harder than previously estimated may provide stronger evidence of your ability. Your overall mastery depends on the full pattern of your answers, so the effect can go in either direction.

A small Monday adjustment does not mean you have suddenly become better or worse at maths. It means the system has revised its estimate using more evidence.

Your submitted answers and raw marks are not changed by recalibration. What changes is how the model interprets those results when estimating your mastery. You do not need to retake a paper or do anything to receive the update.

How should I interpret these changes?

Try to focus on your progress over time rather than a small movement after an individual update. Mastery is a useful guide to your current level, and the range shown alongside it is a reminder that any ability estimate carries some uncertainty.

For more about the model and which attempts count, see How your mastery score works.

— Joe