What minimum coverage probability is required for expanded uncertainty under ANAB supplemental standards?

The correct answer is 95%. In the context of expanded uncertainty under ANAB supplemental standards, a minimum coverage probability of 95% is stipulated. This means that when performing calculations of uncertainty, the aim is to provide a confidence level that captures the true value within the stated range 95% of the time. Setting this standard helps ensure that measurement results are reliable and can be trusted to reflect the true conditions being measured.

Obtaining a 95% coverage probability is a widely accepted practice in various fields, including metrology and quality assurance, and it strikes a balance between practical usability and scientific rigor. Lower coverage probabilities, such as 85% or 90%, may provide less assurance that the measurements accurately reflect the actual conditions. Higher coverage probabilities, like 99%, while providing greater assurance, may require significantly wider intervals, which can reduce precision and utility in practical applications. Thus, 95% serves as a practical threshold for ensuring that results are both reliable and actionable while adhering to ANAB standards.