Step 1: Understanding the question.
The question asks about the function that ensures the accuracy of standards, which refers to measuring performance against set criteria.
Step 2: Analyzing the options.
- Directing: Directing involves motivating and guiding employees, but does not involve judging the accuracy of standards.
- Organising: Organising involves arranging resources and tasks but does not directly judge standards.
- Planning: Planning sets the standards but does not directly evaluate them.
- Controlling: Controlling involves monitoring performance, comparing it to standards, and taking corrective actions when necessary, thus ensuring the accuracy of standards.
Step 3: Conclusion.
The correct answer is Controlling, as it involves evaluating the performance against established standards.
Final Answer:
\[
\boxed{\text{The correct answer is (4) Controlling.}}
\]