Uncertainty

• Combining Measurement Uncertainty Using the GUM Method

So, let’s assume that you are estimating measurement uncertainty. You have identified the influencing factors, quantified the magnitude of their contribution, and reduced them to a standard uncertainty. Now, if you are wondering what the next step is, it is to combine the independent uncertainty components to calculate ‘Combined Uncertainty.’ This is the step […]

• 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 the summation of the independently calculated degrees of freedom. Instead, we must use the Welch Satterthwaite approximation equation to calculate the effective degrees of freedom. In […]

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• UUT Resolution Uncertainty For Different Types of Test Equipment

Quantifying UUT resolution uncertainty can vary significantly depending upon a device’s design, functionality, and operation. The resolution of a digital device may not be evaluated in the same manner as an analog device or artifact. Additionally, the resolution of similar devices may vary depending on how it is used. This makes the evaluation of resolution uncertainty […]

• 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 […]

• Uncertainty Budget Definitions

In 2013,  business has been great! I increased my client-base, my bottom-line, and the awareness of my company, ISOBUDGETS LLC. As a result, I have received a lot of questions this year, from both clients and assessors, regarding the definitions of the terms used in my reports. Therefore, I have decided to create this post in order […]

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• 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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• Rounding Uncertainty in Measurement

Rounding uncertainty in measurement has recently become a topic of great debate. For several years, many Accreditation Bodies (AB) and assessors have asserted the implementation of the ’round up’ method, which forced Certified Accredited Bodies (CAB) to round up their estimated Calibration and Measurement Capability (CMC) values. Although this method of rounding is acceptable, it […]

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• How To Collect Type A Data for Uncertainty Analysis

From my observations, laboratories are having a difficult time calculating and estimating measurement uncertainty. One of the most common problems that I encounter is laboratories are not performing variability studies (i.e. collecting type A data, Gauge R&R, etc.). As a result, there is very little data to generate confident estimates of uncertainty in measurement results. […]

• 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 […]