Percentage Uncertainty Confusion
Hello
I have come accross some contradicting things about percentage uncertainty that I want to clear up.
I have been given an equation which goes like:
Percentage Error = (accepted value - experimental value)/accepted value *100
Then another
Percentage Error = Uncertainty in the value/value * 100.
What im confused about is why they use the same word for different equations. I always thought the second one would be the percentage uncertainty of an apparatus. To work out the total % uncertainty (and total percentage error?) you would add up each individual % uncertainty.
But what confuses me is that they use percentage error interchangably between those two equations but later they evaluate the results from these equations like this:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. If the % uncertainty is smaller than the percentage error. Then other errors may have occurred that resulted in the incorrect value obtained.
I am doing AQA A Level Chemistry and I was wondering if someone could clear up the confusion.
I have come accross some contradicting things about percentage uncertainty that I want to clear up.
I have been given an equation which goes like:
Percentage Error = (accepted value - experimental value)/accepted value *100
Then another
Percentage Error = Uncertainty in the value/value * 100.
What im confused about is why they use the same word for different equations. I always thought the second one would be the percentage uncertainty of an apparatus. To work out the total % uncertainty (and total percentage error?) you would add up each individual % uncertainty.
But what confuses me is that they use percentage error interchangably between those two equations but later they evaluate the results from these equations like this:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. If the % uncertainty is smaller than the percentage error. Then other errors may have occurred that resulted in the incorrect value obtained.
I am doing AQA A Level Chemistry and I was wondering if someone could clear up the confusion.
Reply 1
Original post
by SenpaiMicroHello
I have come accross some contradicting things about percentage uncertainty that I want to clear up.
I have been given an equation which goes like:
Percentage Error = (accepted value - experimental value)/accepted value *100
Then another
Percentage Error = Uncertainty in the value/value * 100.
What im confused about is why they use the same word for different equations. I always thought the second one would be the percentage uncertainty of an apparatus. To work out the total % uncertainty (and total percentage error?) you would add up each individual % uncertainty.
But what confuses me is that they use percentage error interchangably between those two equations but later they evaluate the results from these equations like this:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. If the % uncertainty is smaller than the percentage error. Then other errors may have occurred that resulted in the incorrect value obtained.
I am doing AQA A Level Chemistry and I was wondering if someone could clear up the confusion.
I have come accross some contradicting things about percentage uncertainty that I want to clear up.
I have been given an equation which goes like:
Percentage Error = (accepted value - experimental value)/accepted value *100
Then another
Percentage Error = Uncertainty in the value/value * 100.
What im confused about is why they use the same word for different equations. I always thought the second one would be the percentage uncertainty of an apparatus. To work out the total % uncertainty (and total percentage error?) you would add up each individual % uncertainty.
But what confuses me is that they use percentage error interchangably between those two equations but later they evaluate the results from these equations like this:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. If the % uncertainty is smaller than the percentage error. Then other errors may have occurred that resulted in the incorrect value obtained.
I am doing AQA A Level Chemistry and I was wondering if someone could clear up the confusion.
Quote
Percentage Error = Uncertainty in Value / Value * 100 is false; whereas Percentage Error = (Accepted Value - Experimental Value)/ Accepted Value * 100 is true.
Note #1: Percentage Error (PE) is a percentage measure of how far your experimental value is from the true value.
Unquote
Read Percentage Uncertainty (PU) = Uncertainty in the value / value * 100 instead of Percentage Error = Uncertainty in the value/value * 100.
Note #2: PU indicates the range of values within which the true value is most likely to fall, and serves as a measure of the uncertainty in your experimental value.
For example, if an apparatus has a percentage uncertainty of 5%, it means that the true value is likely to be within 5% of the measured value.
I hope I have been of some help. If you are still struggling after these little hints, you may need more detailed guidance. In this case, I will ask you to clarify what is unclear and provide further explanations to help you understand the solution.
Bye,
Sandro
Reply 2
Original post
by NitrotolueneQuote
Percentage Error = Uncertainty in Value / Value * 100 is false; whereas Percentage Error = (Accepted Value - Experimental Value)/ Accepted Value * 100 is true.
Note #1: Percentage Error (PE) is a percentage measure of how far your experimental value is from the true value.
Unquote
Read Percentage Uncertainty (PU) = Uncertainty in the value / value * 100 instead of Percentage Error = Uncertainty in the value/value * 100.
Note #2: PU indicates the range of values within which the true value is most likely to fall, and serves as a measure of the uncertainty in your experimental value.
For example, if an apparatus has a percentage uncertainty of 5%, it means that the true value is likely to be within 5% of the measured value.
I hope I have been of some help. If you are still struggling after these little hints, you may need more detailed guidance. In this case, I will ask you to clarify what is unclear and provide further explanations to help you understand the solution.
Bye,
Sandro
Percentage Error = Uncertainty in Value / Value * 100 is false; whereas Percentage Error = (Accepted Value - Experimental Value)/ Accepted Value * 100 is true.
Note #1: Percentage Error (PE) is a percentage measure of how far your experimental value is from the true value.
Unquote
Read Percentage Uncertainty (PU) = Uncertainty in the value / value * 100 instead of Percentage Error = Uncertainty in the value/value * 100.
Note #2: PU indicates the range of values within which the true value is most likely to fall, and serves as a measure of the uncertainty in your experimental value.
For example, if an apparatus has a percentage uncertainty of 5%, it means that the true value is likely to be within 5% of the measured value.
I hope I have been of some help. If you are still struggling after these little hints, you may need more detailed guidance. In this case, I will ask you to clarify what is unclear and provide further explanations to help you understand the solution.
Bye,
Sandro
Hello, thank you very much for taking the time to clarify. I have attempted to understand it a bit more and I have come up with these notes. I apologies if it is a bit long, but if possible could you just let me know if they are correct as I just want to ensure my understanding is right.
I also have one further question: There are 3 pictures of a PMT revision page at the bottom. I was wondering when we would use these techniques if they are even used at all. (i.e the combining uncertainties, repeated measurements and significant figure uncertainty.
Thank you very much again,
Max
Notes:
Errors and Uncertainties:
Uncertainty:
Every time you measure something using an apparatus there is a small uncertainty associated with the value you obtain. An (absolute) uncertainty is the range in which the true value is likely to fall. E.g if we have 25cm^3 +-0.5 it means that the true value could be 25.5 or 24.5.
For measurements where we take the difference between two readings, we must add the uncertainty of the apparatus of each reading, since it is the same apparatus we can just multiply by 2.
This is due to the rule where if we are adding or subtracting two measurements, we must add the absolute measurement uncertainties.
For any incremented apparatus, such as a burette, thermometer. The uncertainty is half the smallest division. If a graduation on the burette is 0.1, the uncertainty will be +-0.05.
Uncertainties are quoted to 1 SF.
We can work out the percentage uncertainty for a certain apparatus using:
The percentage uncertainty displays the significance of an absolute uncertainty compared to the measurement we took. The larger the value, the larger the effect that the uncertainty has on the measurement, meaning that the measured value is less accurate to the true value.
We may be asked to calculate the total percentage uncertainty of an experiment. This is achieved by adding up all percentage uncertainties of each individual apparatus. The larger the number the less accurate our overall experimental result is.
Error:
An error is the difference between a measured value and the true value. We can work out the percentage error which displays the error in a better way.
The greater the value, the greater the difference between the measured value and the true value. We can compare the total percentage uncertainty and the percentage error as below:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. Therefore the experiment could be improved by using apparatus with higher resolutions.
If the % uncertainty is smaller than the percentage error. Then other factors have influenced the experiment so that the measured value is not the same as the true value.
Reducing the % uncertainty (and subsequently the % error):
•
Using more accurate (higher resolution) apparatus with smaller uncertainties.
•
Increasing the mass/volume of the substance measured will give a smaller % uncertainty. Leads to a more accurate result.
------
Repeated Measurements:
In an exam, a question may be asked to find the uncertainty of the mean value of some data including outliers. As soon as you see the outliers part you can use this technique:
Combining Uncertainties:
Additional Information:
Reply 3
Original post
by NitrotolueneQuote
Percentage Error = Uncertainty in Value / Value * 100 is false; whereas Percentage Error = (Accepted Value - Experimental Value)/ Accepted Value * 100 is true.
Note #1: Percentage Error (PE) is a percentage measure of how far your experimental value is from the true value.
Unquote
Read Percentage Uncertainty (PU) = Uncertainty in the value / value * 100 instead of Percentage Error = Uncertainty in the value/value * 100.
Note #2: PU indicates the range of values within which the true value is most likely to fall, and serves as a measure of the uncertainty in your experimental value.
For example, if an apparatus has a percentage uncertainty of 5%, it means that the true value is likely to be within 5% of the measured value.
I hope I have been of some help. If you are still struggling after these little hints, you may need more detailed guidance. In this case, I will ask you to clarify what is unclear and provide further explanations to help you understand the solution.
Bye,
Sandro
Percentage Error = Uncertainty in Value / Value * 100 is false; whereas Percentage Error = (Accepted Value - Experimental Value)/ Accepted Value * 100 is true.
Note #1: Percentage Error (PE) is a percentage measure of how far your experimental value is from the true value.
Unquote
Read Percentage Uncertainty (PU) = Uncertainty in the value / value * 100 instead of Percentage Error = Uncertainty in the value/value * 100.
Note #2: PU indicates the range of values within which the true value is most likely to fall, and serves as a measure of the uncertainty in your experimental value.
For example, if an apparatus has a percentage uncertainty of 5%, it means that the true value is likely to be within 5% of the measured value.
I hope I have been of some help. If you are still struggling after these little hints, you may need more detailed guidance. In this case, I will ask you to clarify what is unclear and provide further explanations to help you understand the solution.
Bye,
Sandro
Are you a bot?
or are you just using AI to answer the questions?
Reply 4
Original post
by SenpaiMicroHello, thank you very much for taking the time to clarify. I have attempted to understand it a bit more and I have come up with these notes. I apologies if it is a bit long, but if possible could you just let me know if they are correct as I just want to ensure my understanding is right.
I also have one further question: There are 3 pictures of a PMT revision page at the bottom. I was wondering when we would use these techniques if they are even used at all. (i.e the combining uncertainties, repeated measurements and significant figure uncertainty.
Thank you very much again,
Max
Notes:
Errors and Uncertainties:
Uncertainty:
Every time you measure something using an apparatus there is a small uncertainty associated with the value you obtain. An (absolute) uncertainty is the range in which the true value is likely to fall. E.g if we have 25cm^3 +-0.5 it means that the true value could be 25.5 or 24.5.
For measurements where we take the difference between two readings, we must add the uncertainty of the apparatus of each reading, since it is the same apparatus we can just multiply by 2.
This is due to the rule where if we are adding or subtracting two measurements, we must add the absolute measurement uncertainties.
For any incremented apparatus, such as a burette, thermometer. The uncertainty is half the smallest division. If a graduation on the burette is 0.1, the uncertainty will be +-0.05.
Uncertainties are quoted to 1 SF.
We can work out the percentage uncertainty for a certain apparatus using:
The percentage uncertainty displays the significance of an absolute uncertainty compared to the measurement we took. The larger the value, the larger the effect that the uncertainty has on the measurement, meaning that the measured value is less accurate to the true value.
We may be asked to calculate the total percentage uncertainty of an experiment. This is achieved by adding up all percentage uncertainties of each individual apparatus. The larger the number the less accurate our overall experimental result is.
Error:
An error is the difference between a measured value and the true value. We can work out the percentage error which displays the error in a better way.
The greater the value, the greater the difference between the measured value and the true value. We can compare the total percentage uncertainty and the percentage error as below:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. Therefore the experiment could be improved by using apparatus with higher resolutions.
If the % uncertainty is smaller than the percentage error. Then other factors have influenced the experiment so that the measured value is not the same as the true value.
Reducing the % uncertainty (and subsequently the % error):
------
Repeated Measurements:
In an exam, a question may be asked to find the uncertainty of the mean value of some data including outliers. As soon as you see the outliers part you can use this technique:
Combining Uncertainties:
Additional Information:
I also have one further question: There are 3 pictures of a PMT revision page at the bottom. I was wondering when we would use these techniques if they are even used at all. (i.e the combining uncertainties, repeated measurements and significant figure uncertainty.
Thank you very much again,
Max
Notes:
Errors and Uncertainties:
Uncertainty:
Every time you measure something using an apparatus there is a small uncertainty associated with the value you obtain. An (absolute) uncertainty is the range in which the true value is likely to fall. E.g if we have 25cm^3 +-0.5 it means that the true value could be 25.5 or 24.5.
For measurements where we take the difference between two readings, we must add the uncertainty of the apparatus of each reading, since it is the same apparatus we can just multiply by 2.
This is due to the rule where if we are adding or subtracting two measurements, we must add the absolute measurement uncertainties.
For any incremented apparatus, such as a burette, thermometer. The uncertainty is half the smallest division. If a graduation on the burette is 0.1, the uncertainty will be +-0.05.
Uncertainties are quoted to 1 SF.
We can work out the percentage uncertainty for a certain apparatus using:
The percentage uncertainty displays the significance of an absolute uncertainty compared to the measurement we took. The larger the value, the larger the effect that the uncertainty has on the measurement, meaning that the measured value is less accurate to the true value.
We may be asked to calculate the total percentage uncertainty of an experiment. This is achieved by adding up all percentage uncertainties of each individual apparatus. The larger the number the less accurate our overall experimental result is.
Error:
An error is the difference between a measured value and the true value. We can work out the percentage error which displays the error in a better way.
The greater the value, the greater the difference between the measured value and the true value. We can compare the total percentage uncertainty and the percentage error as below:
If the total % uncertainty due to the apparatus > the percentage error: (or if it is similar) it is likely that the difference in the values is due to the uncertainty in the apparatus. Therefore the experiment could be improved by using apparatus with higher resolutions.
If the % uncertainty is smaller than the percentage error. Then other factors have influenced the experiment so that the measured value is not the same as the true value.
Reducing the % uncertainty (and subsequently the % error):
•
Using more accurate (higher resolution) apparatus with smaller uncertainties.
•
Increasing the mass/volume of the substance measured will give a smaller % uncertainty. Leads to a more accurate result.
------
Repeated Measurements:
In an exam, a question may be asked to find the uncertainty of the mean value of some data including outliers. As soon as you see the outliers part you can use this technique:
Combining Uncertainties:
Additional Information:
Hello Max!
From what you've written, it seems like you have a good grasp of the concepts:
Uncertainty
1.
Your understanding of what is associated with measurements is correct.
2.
You are correct in understanding the uncertainty associated with repeated measurements.
3.
As for incremented apparatus, your understanding is correct.
4.
Your understanding is correct about Percentage Uncertainty = Uncertainty in value / value * 100.
1.
Your understanding is correct in every respect.
__________________________________
Good night,
Sandro
Reply 5
Original post
by charcoAre you a bot?
or are you just using AI to answer the questions?
or are you just using AI to answer the questions?
In this case it was an Italian text in which I studied the 'theory of error' in the field of measurement. So neither bot nor AI was used. I translated what I needed from Italian to English and posted it.
PS: Do you find me unsympathetic?
Bye,
Sandro
Reply 6
Original post
by NitrotolueneHello Max!
From what you've written, it seems like you have a good grasp of the concepts:
UncertaintyErrorOn the subject of "Repeated Measurements", I'll answer tomorrow, it's getting late for me at least.
Good night,
Sandro
From what you've written, it seems like you have a good grasp of the concepts:
Uncertainty
1.
Your understanding of what is associated with measurements is correct.
2.
You are correct in understanding the uncertainty associated with repeated measurements.
3.
As for incremented apparatus, your understanding is correct.
4.
Your understanding is correct about Percentage Uncertainty = Uncertainty in value / value * 100.
1.
Your understanding is correct in every respect.
__________________________________
Good night,
Sandro
Thank you very much!
I missread the other person who posted earlier, I thought he said you were a verified bot but that isnt the case as you have given me very detailled help. I appreciate the aid and thank you again for attempting to help me even with the language barrier.
(edited 1 year ago)
Reply 7
Original post
by NitrotolueneIn this case it was an Italian text in which I studied the 'theory of error' in the field of measurement. So neither bot nor AI was used. I translated what I needed from Italian to English and posted it.
PS: Do you find me unsympathetic?
Bye,
Sandro
PS: Do you find me unsympathetic?
Bye,
Sandro
Strange - running your answers through AI detection software gives 70% likelihood of AI Generated Text.
Maybe AI stands for Answers in Italian ...
Reply 8
Good morning charco!
Stop chat...
Let us be friends!😀
Regards,
Sandro
Stop chat...
Let us be friends!😀
Regards,
Sandro
Reply 9
yall on smin
Quick Reply
Related discussions
- Confused with deducing uncertainties from equipment
- percentage uncertainty aqa 2019 paper 1
- A level OCR A precision
- Edexcel A-level Physics Paper 3 - 17th June 2025 [Exam Chat]
- gcse paper 1 chem
- Wjec AS chemistry unit 1
- cardiff uni changes
- Magnetic Fields - AQA Physics June 2023 - Paper 3 - Question doubt
- ARU
- UCAS Education section as an American student
- Grade 12 CBSE Predicted Grades
- Confused what to do next?????resit?? ucl??
- 'what do you want to do after uni?' - the question every student dreads
- Questions about Islam
- uni accommodation / firming
- OCR GCSE Physics A Paper 4 Higher - 14 June 2024 [Exam Chat]
- Sodium Thiosulfate and Hydrochloric Acid. Why is it zero order?
- Turnitin AI score
- Should I drop English Lit or Psychology for A levels
- engineering personal statement
Latest
Trending
Last reply 1 week ago
AQA A level chemistry synthetic routes map - what is the best one to memorise?Last reply 5 months ago
AQA Chemistry Electrode Potentials Conventional Representation QuestionLast reply 7 months ago
OCR B Salters A Level Chemistry 2025 Advanced ArticleLast reply 8 months ago
Help with this chemistry question? (A2, acid-base equilibria)
How The Student Room is moderated
To keep The Student Room safe for everyone, we moderate posts that are added to the site.
