Start where you are.
Maths builds on itself. Find where you are in it, and you won’t repeat what you know or miss what you need.
In plain words
Almost every idea in maths sits on top of others. You can’t work with fractions until you can multiply, and percentages need fractions. Something you need first is called a prerequisite.
Those links make testing faster. If you can add two fractions, you can almost certainly multiply whole numbers. So one well-chosen question tells you about several concepts at once, and a short test can place you across a whole subject.
It works a bit like the game Twenty Questions. Each good question rules out a large group of answers, so you get to the right one in far fewer steps than asking about everything.
What the researchers did
Evidence: established method
In 1985 two mathematicians, Jean-Paul Doignon and Jean-Claude Falmagne, set out a way to describe what a person knows in a subject. It treats knowledge as the set of problems you can solve, and uses the links between problems to rule out combinations that can’t happen.
In a later paper the same group showed how much this narrows things down. For 24 algebra problems there are about 16.8 million possible combinations of known and unknown. Using an expert’s judgement of which problems depend on which, and then testing, they cut that to 312.
This theory is the basis of ALEKS, a maths system that adapts to each student. Its creators say millions of students have used it. ALEKS’s own researchers report that its placement test asks at most 16 questions to estimate what a student knows across up to 501 topics.
What Consiliae does
Our maths map has 1,424 concepts in 9 chapters, from basic arithmetic to linear algebra. 2,812 links between them record which concept you need first.
The Knowledge Scan asks up to 25 questions before you sign up. Once you have an account, the full scan asks up to 40. It asks at least 10 unless it runs out of things to ask, and after that it stops early once more questions would barely change the picture.
After each answer it updates the chance that you know each concept. A right answer raises the chance for the concepts underneath. A wrong answer, or tapping “I don’t know”, lowers it for the concepts built on top. The next question goes to a concept it hasn’t asked about and is still unsure of, chosen to split what is left to find out.
A concept you were asked about counts as known only if you got it right, the chance you know it reaches 95%, and a second piece of evidence agrees, such as a right answer on a concept built on it. The concepts underneath one you clearly know are counted as known too, so the scan doesn’t need to ask about each of them. Anything it is unsure of stays on your route as a normal lesson.
What this does not prove
Knowledge Space Theory is a piece of mathematics for describing knowledge. It was never tested in one single experiment. The evidence that short adaptive tests place students well comes mostly from ALEKS’s own staff.
Real maths is messier than any map. Sometimes you can learn a skill from more than one set of earlier skills. How accurately our scan places people on our map is something we still have to measure.
Read the research (4)
- Doignon, J.-P., & Falmagne, J.-C. (1985). Spaces for the assessment of knowledge. International Journal of Man-Machine Studies, 23(2), 175-196.
- Falmagne, J.-C., Koppen, M., Villano, M., Doignon, J.-P., & Johannesen, L. (1990). Introduction to knowledge spaces: How to build, test, and search them. Psychological Review, 97(2), 201-224.
- Doignon, J.-P., & Falmagne, J.-C. (2015). Knowledge spaces and learning spaces. arXiv:1511.06757.
- Matayoshi, J., Cosyn, E., Lechuga, C., & Uzun, H. (2024). An evaluation of a placement assessment for an adaptive learning system. Proceedings of the 17th International Conference on Educational Data Mining. (The authors work for McGraw Hill ALEKS.)

