I'm confused on which equation gives percentage uncertainty

In summary: The standard uncertainty of a slope is typically in units of percentage point, while an absolute uncertainty is in terms of the actual value of the parameter.
  • #1
homeworkhelpls
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im confused about the difference of this equation:
1665243195922.png

and this one:
1665243195935.png

which gives percentage uncertainty, so which one should be used to calculate the uncertainty?
 
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  • #2
Are you trying to compute the average gradient?

or are you trying to find the best line through a set of data points plotted in XY form?
 
  • #3
my bad I am trying to find the uncertainty from the graph
 
  • #4
The two equations are out of context but my guess is that they refer to different methods of determining the slope (gradient). It looks like the second equation assumes that one knows the best line (determined how?) while the first equation assumes that one draws two eyeballed straight lines that pass reasonably well over the data such that the best line has a slope between them. Which one you use depends on your method of finding the best line.
 
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  • #5
kuruman said:
The two equations are out of context but my guess is that they refer to different methods of determining the slope (gradient). It looks like the second equation assumes that one knows the best line (determined how?) while the first equation assumes that one draws two eyeballed straight lines that pass reasonably well over the data such that the best line has a slope between them. Which one you use depends on your method of finding the best line.
no sorry bro i don't think you understand it very well i mean the uncertainty and best fit is just determined by drawing the line, thanks for the help though
 
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  • #6
It almost certainly looks like a simplified procedure that likely overestimates the uncertainty.
 
  • #7
homeworkhelpls said:
which one should be used to calculate the uncertainty?
I assume that you mean the standard uncertainty of the slope.

You have not provided enough information. What do these max and min slopes represent? Are they slopes from a 95% confidence interval around the fitted slope parameter. Are they slopes takin men directly from the data? Do you have any other estimate that could describe the statistical distribution from which these slopes are drawn?
 
  • #8
Hint: Think about the units.

What units would you expect a percentage uncertainty to have versus an absolute uncertainty?
 

What is percentage uncertainty and why is it important?

Percentage uncertainty is a measure of the amount of error or variation in a measurement. It is important because it helps us understand the reliability and accuracy of our data.

How do I calculate percentage uncertainty?

Percentage uncertainty is calculated by dividing the absolute uncertainty by the measured value and multiplying by 100. The absolute uncertainty is the smallest division on the measuring instrument used.

What is the difference between percentage uncertainty and absolute uncertainty?

Percentage uncertainty is a relative measure, expressed as a percentage of the measured value, while absolute uncertainty is an absolute measure in the same units as the measured value.

Which equation should I use to calculate percentage uncertainty?

The equation for calculating percentage uncertainty is the same regardless of the type of measurement or instrument used. However, the method for determining the absolute uncertainty may vary depending on the situation.

Can I use percentage uncertainty to compare measurements from different instruments?

Yes, percentage uncertainty can be used to compare measurements from different instruments as it is a relative measure. However, it is important to note that the absolute uncertainty may vary between instruments, so it is important to consider both values when making comparisons.

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