3.5.9 - Percentage uncertainty

Determine percentage uncertainty for a single reading using half the instrument resolution and for repeated readings using half the range; compounding percentage uncertainties is not required in Unit 3.

Use - percentage uncertainty to connect the rule to the data and decision in the question.

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

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

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