Uncertainty: Systematic & Random

AI Thread Summary
Absolute uncertainty is defined as the total amount by which a measured value may differ from the actual value, contrasting with fractional uncertainty, which is the ratio of absolute uncertainty to the measured value. The discussion highlights a preference for the term "systematic error" over "systematic uncertainty," suggesting that total error comprises both systematic and random components. In repeated measurements of the same quantity, these errors can be interpreted as either fractional or absolute. When measuring different quantities, the nature of these errors may change, with systematic errors potentially remaining constant in fractional terms while random errors may be constant in absolute terms. The conversation emphasizes the complexity of understanding and categorizing measurement errors.
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Homework Statement
Dose anybody please know what the relationship between absolute uncertainty, systematic uncertainty and random uncertainty is?
Relevant Equations
Equation above.
I am thinking that it might could be absolute uncertainty = systematic uncertainty + random uncertainty.

Many thanks!
 
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Any particular reason ?
 
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As far as I am aware, absolute uncertainty means the absolute amount by which the measured value may differ from the actual value. This is as opposed to fractional uncertainty, which is absolute uncertainty divided by the measured value.
And I find "systematic uncertainty" conceptually awkward. Systematic error is the more usual expression.
So I would say that total error is systematic + random, where each of those may be (consistently) interpreted as fractional or absolute.

That is with regard to repeated measurements which are in principle of the same quantity. If they are for different quantities (because some parameter is being varied) these errors may vary in different ways. E.g. the systematic fractional error my remain constant, while for random error it is the absolute error that is constant.
 
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BvU said:
Any particular reason ?
haruspex said:
As far as I am aware, absolute uncertainty means the absolute amount by which the measured value may differ from the actual value. This is as opposed to fractional uncertainty, which is absolute uncertainty divided by the measured value.
And I find "systematic uncertainty" conceptually awkward. Systematic error is the more usual expression.
So I would say that total error is systematic + random, where each of those may be (consistently) interpreted as fractional or absolute.

That is with regard to repeated measurements which are in principle of the same quantity. If they are for different quantities (because some parameter is being varied) these errors may vary in different ways. E.g. the systematic fractional error my remain constant, while for random error it is the absolute error that is constant.
Thank you for your replies @BvU and @haruspex!

@BvU I can't remember now sorry.

@haruspex thank you that helps

Many thanks!
 
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