Estimating Future Velocity w/ Radar Gun & Internal Error

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Discussion Overview

The discussion revolves around estimating future velocity measurements using a radar gun that has an internal error. Participants explore how changes in the mean of the measurements might affect the standard deviation and what additional data might be necessary for accurate predictions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the new radar gun will have an internal error of roughly 1 m/s and questions how to scale the standard deviation from the previous measurements.
  • Another participant argues that a change in the mean does not necessarily affect the standard deviation, providing an example to illustrate this point.
  • Some participants express uncertainty about whether it makes sense to scale the standard deviation without additional information regarding the variance.
  • It is proposed that knowing if the variance has changed is crucial for determining whether the standard deviation should be adjusted.
  • One participant reflects on the limitations of mathematical predictions in the context of uncertainty, suggesting that educated guesses may be the best approach until more is understood about underlying theories.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the standard deviation should be scaled with the change in mean, and multiple competing views remain regarding the necessity of additional data for accurate predictions.

Contextual Notes

Participants note the importance of understanding the relationship between mean and standard deviation, as well as the need for more data to establish future variance and standard deviation accurately.

NoobixCube
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Suppose I have a radar gun that can measure velocity with an internal error with a mean of 3 m/s and a standard deviation of 1m/s on that error
eg velocity
10 +- 2.8
6 +- 3.1
21 +- 3.2and so on. Now I want to make a prediction of the future when I get a new radar gun. It will have an internal error of roughly 1m/s
How then do I scale the std deviation? by a factor of three?
Thanks all!
 
Last edited:
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A change in the mean doesn't have to change the standard deviation.
The standard deviation could still be 1m/s.

For example {3,4,5,3,4,5} and {7,8,9,7,8,9} have the same standard deviation but different means.

You really need more data to establish a future variance and standard deviation.
 
If you were to make an educated guess would it make sense to scale the std?
What other data would you need?
 
NoobixCube said:
If you were to make an educated guess would it make sense to scale the std?

No, not without more information.

NoobixCube said:
What other data would you need?

You need to know if the variance has changed.

If your future radar gun is no more precise, but simply more accurately calibrated, your average will change but the variance and std.dev. will not.
 
I would think that math could explain & tell every little detail about the future, however I think that you would have to have an equation for everything, so until this "Quantum Theory" stuff is solved. Until then, I think all you 'can' do is make an educated guess. : )
 
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