# Analysis

• ### Calculating Effective Degrees of Freedom

When performing uncertainty analysis, it is important to calculate the degrees of freedom associated with the estimation of uncertainty. However, determining the total degrees of freedom is not simply adding together all of your independently calculated degrees of freedom. Instead, you must use the Welch Satterthwaite approximation equation to calculate the effective degrees of freedom. […]

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• ### 5 Best Calibration Interval Guides You Need To Read

Recently, there have been a lot questions and discussion regarding calibration intervals. People want to know how to establish and adjust calibration intervals appropriately. Well, there is not one single method that will apply to all or most situations. Therefore, I recommend that you study as many methods of Calibration Interval Analysis as possible to […]

• ### Conformance to Specifications and Statements of Conformance

Assessing Conformance to Specifications When a client requires a statement of conformance to predetermined specifications, there are several cases where the uncertainty in measurement has an influence on the statement of conformance. To properly assess conformance, add(subtract) the estimated expanded uncertainty to(from) the measurement result and determine which of the four following scenarios apply. […]

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• ### Propagation of Uncertainty Rules for Estimating Uncertainty

Propagation of Uncertainty Propagation of uncertainty is a method that transmits the uncertainties of independent variables through an equation to estimate the uncertainty of the final calculation. When physical quantities cannot be measured with a single direct measurement, we typically perform indirect measurements of two or more quantities to calculate the desired measurement result. By […]

• ### How to Propagate Uncertainty for ISO/IEC 17025

Propagation of uncertainty is an important aspect of uncertainty analysis. It is a method that transmits the uncertainties of independent variables through an equation to estimate the uncertainty of the final calculation. Commonly practiced in error and uncertainty analysis, the method is useful for estimating uncertainty where physical quantities cannot be measured directly.   Indirect […]

• ### How to Perform a Repeatability Test 3:

Collecting Data Before you can analyze and evaluate the measurement system and process, you must collect some data. However, before diving in head first, there are some things that should be considered. Review the Plan First, review your plan. If you do not, you may find yourself repeating the experiment. It is more time efficient […]

• ### 6 Influences on Uncertainty in Measurement Results

When performing uncertainty analysis, it is important to consider what influences uncertainty, not errors, in measurement results. Here is a list of six common influences that will bring awareness and enlightenment to all who perform measurements.   01 | Equipment The equipment selected to perform tests and calibrations is important. It can severely impact […]

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• ### How Are Manufacture Specifications Distributed: Gaussian or Uniform

Recently, I encountered several individuals (technical experts) who believed that a manufacturer’s published accuracy specification is characterized by a uniform or rectangular probability distribution. For several years, I have observed the opinions of others who seem to share the same consensus. However, I have never accepted this assumption; so, I thought I would share my […]

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• ### Confidence Intervals and Risk in Measurement

When performing experiments, we expect to achieve an approximation of confidence in the results of our observations. When our confidence is high, we typically expect our risk of failure to be low. Therefore, it is important to understand the importance of confidence and risk when estimating the uncertainty in our measurement results. What is a […]