Uncertainty of a straight line

In summary, the uncertainty in the spring constant can be found by the uncertainty in the gradient of the graph.
  • #1
leo037
2
0

Homework Statement


My teacher assigned a lab report on an experiment where 2 graphs need to be drawn. One graph has some uncertainty which is calculated alright ((slope max - slope min) * 0.5) and the other graph still need to be drawn.. The values of the second graph make a perfect straight line which would make the uncertainty to be 0. how would you calculate the uncertainty?

Homework Equations


The Attempt at a Solution

 
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  • #2
Hi there,

Are you absolutely sure that the graph make a perfect straight line. That would mean that all you experimental measures are precisely on the line. If so, from your experimental measures, you would have not uncertainty.
 
  • #3
Just because the data points fit on a straight line does not mean that there was no uncertainty in the measurements.

You should have error boxes around each point, based on the uncertainties in the measurements of your variables.
 
  • #4
Hi there,

These uncertainties are considered in the measurements of the points.

There is no added uncertainty to the plotting of the graph.

Cheers
 
  • #5
Either I am not understanding this properly, or fatra knows more about the specific task you have been given.

Maybe you could shed some more light on the experiment that you are required to be writing up.

But consider an experiment on Hookes' Law:
You hang weights from a spring and measure the distance it stretches.

To find the spring constant of the spring, you can plot distance vs. weight and find the gradient. The uncertainty in your value for the spring constant can be found by the uncertainty in the gradient of the graph. This can be done as you have described above.

You will have uncertainty in the measurements of weight and in the measurements of distance. These values should allow you to set up error boxes around each point. It is using these boxes that can give you max and min gradient.

Your measured values might end up lying on a straight line - but this does not mean that there is no uncertainty in your measurements!
 

Related to Uncertainty of a straight line

What is the "Uncertainty of a straight line"?

The "Uncertainty of a straight line" refers to the amount of error or variability in the slope and intercept of a straight line that is fitted to a set of data points. It is a measure of how well the line represents the data and can be used to evaluate the reliability of the line's parameters.

How is the uncertainty of a straight line calculated?

The uncertainty of a straight line is typically calculated using a statistical method called linear regression. This involves analyzing the data points and fitting a line that minimizes the sum of the squared distances between the line and the data points. The uncertainty is then determined by the standard error of the slope and intercept of the fitted line.

What factors can affect the uncertainty of a straight line?

The uncertainty of a straight line can be affected by several factors, such as the number of data points, the distribution of the data, and the presence of outliers. It can also be influenced by the method used to calculate the uncertainty, as different methods may give slightly different results.

Why is it important to consider the uncertainty of a straight line?

Considering the uncertainty of a straight line is important because it provides information about the reliability and accuracy of the line. A smaller uncertainty indicates a more precise fit, while a larger uncertainty indicates a less reliable fit. This can be useful in making decisions or drawing conclusions based on the data and the fitted line.

How can the uncertainty of a straight line be reduced?

The uncertainty of a straight line can be reduced by increasing the number of data points, choosing a representative and unbiased sample, and removing outliers if necessary. It can also be reduced by using more sophisticated statistical methods for fitting the line and calculating the uncertainty. However, it is important to note that there will always be some level of uncertainty in a fitted line, as it is impossible to perfectly represent all of the data points.

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