Significant Figures and Uncertainty

Uncertainty

The International Vocabulary of Basic and General Terms in Metrology (VIM) defines uncertainty as:

"A parameter associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand."

NOTE 1: The parameter may be, for example, a standard deviation (or a given multiple of it), or the width of a confidence interval.

NOTE 2: Uncertainty of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results or series of measurements and can be characterized by standard deviations. The other components, which also can be characterized by standard deviations, are evaluated from assumed probability distributions based on experience or other information The ISO Guide refers to these different cases as Type A and Type B estimations respectively.

There are numerous publications concerning uncertainty calculations. I am concerned that many presentations on the topic are written in a language that may be difficult for the beginner to easily grasp. However, there is a clear and complete guide that I highly recommend.

Recommended Reading

Whether you're a beginner or an experienced student of the subject, I strongly encourage you to read Quantifying Uncertainty in Analytical Measurement, published by Eurachem.

Of the numerous volumes of publications on this topic I have seen over the years, this one stands out above all others. It is quite thorough, written in an understandable manner and it includes several good examples.

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