Is my textbook wrong about absolute uncertainties?

  • #1
heroslayer99
33
6
Homework Statement
The Hipparcos space telescope used stellar parallax with a precision of 9.7 × 10–4 arcseconds to
determine the distance to stars. Estimate the maximum stellar distance in parsecs that could be measured using Hipparcos. Calculate the percentage uncertainty in the calculated value of the distance to Polaris A if the parallax angle is 7.5 × 10–3 arcseconds.
Relevant Equations
d = 1/p
First off, I will set out what I think I know so that any misconceptions of mine can be put right.
Definitions:
Precision: a quality denoting the closeness of agreement between (consistency, low variability of) measured values obtained by repeated measurements
Accuracy: A quality denoting the closeness of agreement between a measured value and the true value
Uncertainty: interval within which the true value can be expected to lie
Resolution: Smallest increment on the instrument
In the case of a single reading, the abs uncertainty is half the resolution of the instrument, in the case of a measurement (the difference between two readings) the abs uncertainty is twice that of a single reading (twice the uncertainty in 1 reading is clearly just the resolution). For digital devices, like a voltmeter, approximate the abs uncertainty as half the resolution (same as a single reading).
What confuses me greatly is that in my problem I am told that the "precision" of the telescope is 9.7 x 10^-4, but from what I already know, precision (at least at the level I am working at, and the level that the textbook is written for), cannot be quantified, so I do not know what that value means, most likely it is the resolution, and the author has made a mistake. I am also confused as to whether the abs uncertainty is the quoted "resolution" or half this value. Finally, if this is the resolution then clearly the stated value for the parallax angle would be a multiple of this, turns out it isn't.
Please help :(
 
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  • #2
Why make things difficult (if with a little bit of effort they can be made bloody impossible :wink:) ?

What if the observed parallax is simply ##75 \ \times 10^{-4} \ \ \pm \ 9.7 \ \times 10^{-4}## ? Can you answer the question?

##\ ##
 
  • #3
heroslayer99 said:
Accuracy: A quality denoting the closeness of agreement between a measured value and the true value
According to https://en.wikipedia.org/wiki/Accuracy_and_precision, ISO defines it that way but others limit it to systematic error, making it independent of precision.
Presumably, resolution errors would be categorised as systematic (though by deliberately adding random errors and taking multiple readings they can be converted to random errors and thereby reduced).
heroslayer99 said:
in the case of a measurement (the difference between two readings)
Why would you describe the difference between two readings a "measurement "?

But, yes, I agree with you, it is sloppy. If precision (random error) is the only issue then you can get greater overall accuracy by averaging multiple readings. I would interpret it as here intending uncertainty from whatever cause.
 

1. How do I know if my textbook is wrong about absolute uncertainties?

One way to determine if your textbook is incorrect about absolute uncertainties is to cross-reference the information with reputable sources such as scientific journals, textbooks, or online resources. It is also helpful to consult with your instructor or a subject matter expert for clarification.

2. What should I do if I suspect that my textbook has errors in absolute uncertainties?

If you believe that your textbook contains inaccuracies regarding absolute uncertainties, it is important to raise your concerns with your instructor or academic advisor. They can help you verify the information and provide guidance on how to address any discrepancies.

3. Can I rely on my textbook for accurate information about absolute uncertainties?

While textbooks are generally considered reliable sources of information, errors can occasionally occur. It is always a good idea to verify critical information, such as absolute uncertainties, through additional sources to ensure accuracy.

4. How can I double-check the absolute uncertainties provided in my textbook?

To double-check the absolute uncertainties presented in your textbook, you can perform calculations independently using the given data and formulas. Comparing your results with those in the textbook can help you identify any discrepancies and determine if corrections are necessary.

5. What steps can I take to correct errors in absolute uncertainties in my textbook?

If you discover errors in the absolute uncertainties presented in your textbook, you can notify the publisher or author of the issue. Providing specific details about the errors and supporting evidence can help facilitate the correction process and ensure accurate information for future editions.

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