To recap: The standard you need is ASME PTC 19.1 – Test Uncertainty . Whether you are validating a new gas turbine, commissioning a pump, or just completing a university lab report, this document is your legal and technical roadmap to defensible results.

from the standard, such as the Root-Sum-Square (RSS) method? PTC 19.1 - Test Uncertainty - ASME

You might wonder why you should buy the ASME standard when the is available. Here is the difference:

The ASME Performance Test Codes (PTCs) provide uniform rules for testing mechanical equipment. While other codes focus on specific hardware (like PTC 22 for gas turbines), is a "supplement" that provides the mathematical framework for uncertainty analysis across all performance tests.