Calc Accuracy: Percent Error Within 5%?

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Discussion Overview

The discussion revolves around the interpretation of accuracy and percent error in the context of an experiment measuring the speed of light. Participants explore the definitions of accuracy and precision, the implications of a 5% accuracy requirement, and how it relates to percent error calculations.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether a 5% accuracy requirement means that their percent error should also be within 5%, providing a formula for percent error.
  • Another participant clarifies that accuracy and precision are distinct concepts, suggesting that accuracy refers to how close measurements are to the true value, while precision relates to the repeatability of measurements.
  • A different participant expresses uncertainty about the terminology differences in English compared to their native language, indicating that 'accuracy' and 'precision' may be used interchangeably in their language.
  • Links are shared to resources that explain the difference between accuracy and precision, with one participant seeking verification of the definitions presented in those resources.
  • One participant elaborates on the distinction between accuracy and precision using a target analogy, outlining various scenarios of shooting accuracy and precision.
  • A later reply reiterates the initial question about the 5% accuracy requirement, suggesting that it implies any experimental value should fall within 5% of the accepted value and discusses the importance of minimizing measurement errors to achieve this accuracy.

Areas of Agreement / Disagreement

Participants express differing views on the definitions of accuracy and precision, with some agreeing on their distinctions while others remain uncertain. The interpretation of the 5% accuracy requirement and its relation to percent error is also debated, indicating that no consensus has been reached.

Contextual Notes

There are unresolved assumptions regarding the definitions of accuracy and precision, as well as the specific context in which the 5% accuracy requirement applies. The discussion also highlights potential ambiguities in the terminology used across different languages.

elegysix
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Hello, I'm doing an experiment on the speed of light, and had a simple question.
The manual says accuracy should be within 5% - does this mean the same as my percent error being within 5% ?

percent error being (V-E)/V*100% (V is accepted value, E is measured value)

thanks!
 
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Nope. It means that if you repeat your measurement many times you should obtain results having gaussian distribution of some mean value μ and some standard deviation σ.

Absolute value of difference between your μ and true value [itex]\left| \frac{\mu-V}{V}\right|[/itex] is called relative systematic error, while [itex]\sigma/V[/itex] is a relative statistical error. I don't know to which of those errors your manual refers. If it is not clear: sum of statistical and systematic errors should be smaller than requested value.
 
I thought repeatability was known as precision, while accuracy was a measure of how close it is to the value?
 
Oouu... So we must to wait for explanation by some true Englishman... Maybe you are right - in my language 'accuracy' and 'precision' are exact synonyms, but maybe in English there is a nuance difference. My dictionary doesn't help :confused:
 
here's a link which describes accuracy and precision and the difference. I just want to verify if 5% accuracy means 5% error.

http://webphysics.iupui.edu/NH/Projects/TEAMS%5B2%5D/err6.htm"
 
Last edited by a moderator:
elegysix said:
here's a link which describes accuracy and precision and the difference. I just want to verify if 5% accuracy means 5% error.

http://webphysics.iupui.edu/NH/Projects/TEAMS%5B2%5D/err6.htm"

The statement about the ruler measurement, it says you might expect 12.00+0.01.

Shouldn't that read 12.00 +/- 0.01?

Also, the first statement says to refer to pictures. Even the source code does not have a link. Where is the rest of the reference?
 
Last edited by a moderator:
xts said:
Oouu... So we must to wait for explanation by some true Englishman... Maybe you are right - in my language 'accuracy' and 'precision' are exact synonyms, but maybe in English there is a nuance difference. My dictionary doesn't help :confused:

It is a distinction within physics what the 2 words mean.
If you are shooting at a bull's eye with a projectile, say a gun or arrow:

1. Accurate and precise - All shots hit the center.
2. Acurate but not precise - All shots hit the target anywhere but are distributed
around the centre
3. Not accurate but precise - All shots are distributed off from the centre and
congregate about that spot.
4. Not accurate not precise - Shots show no pattern or no mathematical analysis possible.

Hope that helps.
 
elegysix said:
Hello, I'm doing an experiment on the speed of light, and had a simple question.
The manual says accuracy should be within 5% - does this mean the same as my percent error being within 5% ?

percent error being (V-E)/V*100% (V is accepted value, E is measured value)

thanks!

It would mean that any value you obtain by your experiment should be within 5% of the accepted value.

I would take the percent error as follows:
You percent error would be calculated from the setup of the apparatus. You would maybe be measuring several lengths, frequency, etc, etc and all would have measurement errors.
XTS explains what that entails, and you want to make these errors as small as possible to reach an accuracy of 5% in your experiment. Comparing what you think you should get to what you do get as a measured outcome of the experiment let's you know if your apparatus needs adjustment.
 

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