Lesson 2 - What are the Criteria?

The Unstructured Investigation is assessed against two specific sets of skills: Criterion B (Investigating Patterns) and Criterion C (Communicating). These criteria work together to measure not just whether you found the answer, but how logically and professionally you reached your conclusions.

Criterion B: Investigating Patterns

This criterion measures your ability to act as a mathematical detective. It is divided into several key steps that progress from simple to complex:

Making Predictions (P)

You must show you can spot a trend by filling in missing values in a table for early stages of a pattern. For the highest marks, you need to predict values accurately for later stages that aren't shown in the diagrams, using the patterns in the numbers

Describing Patterns (D)

You need to explain the patterns you see in words. To score well, use "grown-up" mathematical terminology—for example, instead of saying "it adds 3 every time," say it is a linear sequence with a common difference of 3.

Finding the General Rule

This is where you turn your pattern into an algebraic formula (the nth term). The examiners expect to see a rule that works for any stage \(n\).

Testing and Verifying (T & V)

You must check your rule works by testing it with a known value from the table (usually \(n\le 4\)) and verifying it against one of your own later predictions (usually \(n\ge 5\)). You must explicitly state that the calculated value matches the table value.

Justifying and Proving (J)

This is the most challenging part of the investigation. You must explain why the rule works by linking it back to the visual or geometric structure of the problem (for example, showing how the parts of a shape add up to your formula).

Criterion C: Communicating

This criterion is about how "examiner-friendly" your report is. It focuses on the clarity and professionalism of your work:

Mathematical Language and Notation (N)

You must use correct notation and symbols. Avoid "calculator speak"—for instance, always write \(n^{2}\) instead of n^2, and use \(A=4n+1\) instead of "the rule is \(4n+1\)".

Organisation and Coherence (L)

Your work should follow a logical flow so the examiner doesn't have to hunt for your answers. For the highest marks, you must explicitly label your processes by using headings or sentences like "I will now test my rule" or "My rule works because...".

You are also marked on being concise, meaning you should be clear and direct without adding unnecessary or repetitive work.