6.3.4 - Controlling variables

Identify and state how to control all other relevant variables to make an experiment a fair test.

Use - controlling variables to connect the rule to the data and decision in the question.

This matters because - controlling variables determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - controlling variables to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Controlling variables is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.