# Basic uncertainty calculations

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#1
The question is:

The uncertainty in the emf is given as 1.019 +/- 0.001V. Calculate the % uncertainty implied by this data.

I got a value of 0.2% by doing (0.002/1.019)*100. The mark scheme gives the answer as being 0.1%. However, I don't understand this because the variation is +/- 0.001V, so the total possible variation is 0.002V. Why are they only using the variation in one direction to calculate their answer rather than using the total possible variation?
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7 years ago
#2
(Original post by Chlorophile)
The question is:

The uncertainty in the emf is given as 1.019 +/- 0.001V. Calculate the % uncertainty implied by this data.

I got a value of 0.2% by doing (0.002/1.019)*100. The mark scheme gives the answer as being 0.1%. However, I don't understand this because the variation is +/- 0.001V, so the total possible variation is 0.002V. Why are they only using the variation in one direction to calculate their answer rather than using the total possible variation?
Because that's how you define % uncertainty.
If you have an uncertainty of 100 +/- 1 that is termed an uncertainty of plus or minus one part in 100. Or plus or minus 1%
It is always given as half the difference between the max and min values.

Variation and uncertainty are different. They are not asking for variation.
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