How can I calculate uncertainty in my lab report data?

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Discussion Overview

The discussion revolves around calculating uncertainty in lab report data, specifically focusing on different methods for estimating uncertainty based on measurements. Participants explore the application of statistical rules and the implications of measurement tools on uncertainty calculations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Homework-related

Main Points Raised

  • One participant expresses confusion over their uncertainty calculation method compared to their partner's results.
  • Another participant suggests that the uncertainty was calculated using the formula ##\sqrt{2CPM}##.
  • A later reply questions the validity of different methods for calculating uncertainty and seeks clarification on the correct approach.
  • It is noted that uncertainty typically arises from measurement tools or the experimental process itself, and the choice of method may depend on the context of the data.
  • Reference is made to the "square root rule," which states that for large integers, the standard deviation can be approximated as the square root of the number.
  • Assumptions about the meaning of CPM are discussed, suggesting that it relates to counts per minute, which influences the uncertainty calculation.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method for calculating uncertainty, and multiple approaches are discussed without resolution.

Contextual Notes

There are limitations regarding the assumptions made about the data and the definitions of terms like CPM, which may affect the uncertainty calculations. The discussion also highlights the dependence on the measurement tools used.

Hayool
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Hi,

I'm doing a lab report and for every number we need to calculate the uncertainty. I tried to calculate by using the SQRT of the number but i didn't get the same answer as my partner had?
could you help me!

These are the numbers and the uncertainty of my partner which i could not figure out how it was done!

upload_2016-3-1_14-1-27.png
 
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It appears the uncertainty was calculated as
##\sqrt{2CPM}##.
 
RUber said:
It appears the uncertainty was calculated as
Thanks RUber for the fast reply.

Are there any other way to calculate the uncertainty ?
And how can i know I'm using that right way?
 
Normally, the uncertainty comes from your measurement tool, or from the process itself.
Without more information about the expected relationships between your data, I am not sure why you would choose one method over another for uncertainty estimation.

In this document (http://instructor.physics.lsa.umich.edu/int-labs/Statistics.pdf) there is a reference to the "square root rule," which generally says if you know nothing else about a number (large integer), the standard deviation is the square root of the number.

Assuming CPM is a measure of some C per minute, then it might make sense that your count for 2 minutes was 2*CPM.
Then the uncertainty in that measurement would be (using square root rule) ##\sqrt{2 CPM}##.
 

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