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# uncertanity watch

1. how to calculate % uncertainty.what is the formula?
2. (Original post by lopper)
how to calculate % uncertainty.what is the formula?
Do you mean the percentage uncertainty in the value of a measurement due to the apparatus? If you do then it's generally:

3. (Original post by Star-girl)
Do you mean the percentage uncertainty in the value of a measurement due to the apparatus? If you do then it's generally:

The engineer obtained three sets of data. The values for the Young modulus were14.2, 14.7 and 15.1 GPa.Determine the average value and state its uncertainty
4. (Original post by lopper)
The engineer obtained three sets of data. The values for the Young modulus were14.2, 14.7 and 15.1 GPa.Determine the average value and state its uncertainty
Oh, I see - it is uncertainty in the average value of a measurement rather than due to the apparatus.

In that case, have you determined the average value? By how much does the farthest value differ from the average?
5. (Original post by Star-girl)
Oh, I see - it is uncertainty in the average value of a measurement rather than due to the apparatus.

In that case, have you determined the average value? By how much does the farthest value differ from the average?
14.7 Gpa
6. (Original post by lopper)
14.7 Gpa
Yes. Now look at the measured value - which is the one furthest from 14.7 Gpa?
7. will the uncertanity be + or -1/2 range
8. 14.2 and nice the difference is equal to the uncertainty.
9. (Original post by lopper)
14.2 and nice the difference is equal to the uncertainty.
It is indeed. However, you are asked for the percentage uncertainty and this is the difference as a percentage of the mean value.
10. (Original post by Star-girl)
It is indeed. However, you are asked for the percentage uncertainty and this is the difference as a percentage of the mean value.
thanks
11. (Original post by lopper)
thanks
You're welcome.

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