How do you estimate and report measurement uncertainty in your field?

1 What is measurement uncertainty?

Measurement uncertainty is not the same as measurement error, which is the difference between the true value and the measured value of a quantity. Measurement error can be random or systematic, and it can be reduced by improving the accuracy and precision of the instrument and the method. Measurement uncertainty, on the other hand, is an expression of the variability and variability of the measurement results, and it cannot be eliminated completely. Measurement uncertainty reflects the limits of your knowledge and the quality of your data.

2 Why is measurement uncertainty important?

Measurement uncertainty is important for several reasons. First, it helps you to evaluate the reliability and validity of your measurement results, and to identify any sources of uncertainty that may affect them. Second, it helps you to communicate your findings to other researchers and readers, and to compare them with other studies or standards. Third, it helps you to make informed decisions and recommendations based on your data, and to account for any potential risks or errors. Measurement uncertainty is a key aspect of scientific integrity and transparency.

3 How do you estimate measurement uncertainty?

Estimating measurement uncertainty requires different methods and standards based on the field and type of measurement. A common approach is the Guide to the Expression of Uncertainty in Measurement (GUM), which provides a framework and rules for calculating and reporting measurement uncertainty. The GUM method involves identifying the quantity and unit of measurement, defining the measurand, identifying and quantifying sources of uncertainty, classifying them as type A or type B, calculating the standard uncertainty for each source, combining the standard uncertainties, multiplying the combined standard uncertainty by a coverage factor, and reporting the measurement result and expanded uncertainty. This process ensures a 95% confidence interval.

4 How do you report measurement uncertainty?

There are different ways to report measurement uncertainty, depending on your field and the format of your publication. However, a common way is to use the following format:

(measurement result) ± (expanded uncertainty) (unit of measurement) [(coverage factor), (level of confidence)]

For example, if you measure the mass of a sample as 12.34 g, with an expanded uncertainty of 0.05 g, using a coverage factor of 2 and a level of confidence of 95%, you can report it as:

12.34 ± 0.05 g [2, 95%]

Alternatively, you can use parentheses or brackets to indicate the uncertainty, such as:

12.34(5) g or 12.34[5] g

You can also use scientific notation or significant figures to express the uncertainty, such as:

1.234 x 10^1 ± 5 x 10^-2 g or 12.3 ± 0.1 g

You should always follow the guidelines and conventions of your field and your journal when reporting measurement uncertainty, and provide sufficient information and references for your readers to understand and verify your calculations.

5 What are some examples of measurement uncertainty in different fields?

Measurement uncertainty is pertinent to any field involving quantitative measurements, such as physics, chemistry, biology, engineering, and medicine. In physics, measurement uncertainty is usually expressed as a percentage or fraction of the measurement result and calculated using the GUM method. For instance, if you measure the speed of light as 299,792.458 ± 0.001 km/s using a coverage factor of 2 and a level of confidence of 99%, it can be reported as (299,792.458 ± 0.001) km/s [2, 99%] or (299,792.458 ± 3.3 x 10^-7) km/s [2, 99%]. In chemistry, measurement uncertainty is typically expressed as an absolute value or relative standard deviation and calculated using the GUM method. For example, if you measure the concentration of a substance as 0.1234 ± 0.0002 mol/L using a coverage factor of 2 and a level of confidence of 95%, it can be reported as (0.1234 ± 0.0002) mol/L [2, 95%] or (0.1234 ± 0.16%) mol/L [2, 95%]. In biology, measurement uncertainty is usually expressed as a standard error or confidence interval and calculated with statistical methods or models; for instance, if you measure the height of a plant as 12.5 ± 0.3 cm with a standard error of the mean and a 95% confidence interval, it can be reported as 12.5 ± 0.3 cm (95% CI: 11.9 to 13.1 cm) or 12.5 cm (11.9 to 13.1 cm). In engineering, measurement uncertainty is generally expressed as an uncertainty band or tolerance limit and computed using the GUM method; for example, if you measure the diameter of a pipe as 10.00 ± 0.02 mm using a coverage factor of 2 and a level of confidence of 95%, it can be reported as 10.00 ± 0.02 mm [2, 95%] or 10.00 mm (9.98 to 10.02 mm). Lastly, in medicine, measurement uncertainty is generally expressed as a standard deviation or coefficient of variation and calculated with statistical methods or models; for instance, if you measure the blood pressure of a patient as 120 ± 10 mmHg with a standard deviation and coefficient of variation of 8%, it can be reported as 120 ± 10 mmHg (SD:

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?