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In the following course review question I need to choose all the answers that are true about precision and accuracy

1)Definitions of accuracy and precision depend on the type of measurement you are making.

2)Accuracy and precision have the same definition and occur when measurements are close to each other.

3)Accuracy occurs when a measurement is close to the true value and precision occurs when measurements are all close to each other.

4)Accuracy and precision have the same definition and occur when a measurement is close to the true value

5)Precision occurs when a measurement is close to the true value and accuracy occurs when measurements are all close to each other

6)The set of numbers 6.162 cm, 6.163 cm, 6.162 cm is more precise than 6.162 cm, 6.181 cm, 6.150 cm

My solution

I know that 3 is true, accuracy is close to the target and precision is all measurements are close to each other. Therefore number 5 would be false

I know 6 is true because the numbers in the first set are closer than the numbers in the second set

I do not think number 2 is correct, accuracy and precision have two different definitions

I do not think number 4 is correct those definitions are incorrect

Not sure if 1 is correct or not. Looking for some help with this question

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  • $\begingroup$ yes but not to this extent $\endgroup$ Sep 15, 2016 at 22:11
  • $\begingroup$ thanks for the link but still not sure if number 1 is correct or not $\endgroup$ Sep 15, 2016 at 22:19
  • $\begingroup$ okay thnks for your time $\endgroup$ Sep 15, 2016 at 22:32
  • $\begingroup$ No problem, best of luck with it. 99.999 percent sure 1 is incorrect, the definitions should apply to all systems, otherwise they are not worth much as definitions :) $\endgroup$
    – user108787
    Sep 15, 2016 at 22:36
  • $\begingroup$ Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems. $\endgroup$ Sep 16, 2016 at 5:34

1 Answer 1

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Accuracy should always refer to the quality of being "correct," and Precision should always refer to the quality of "uniformity" or "consistency."

All else equal, precision is far more difficult to achieve than accuracy. Once your precision is acceptable, accuracy is typically a simple matter to account for.

For instance, if a marksman manages to hit a target repeatedly half a full meter under his target, but does so in a three centimeter radius circle, then it would be said that his accuracy was particularly poor, but his precision excellent. Being such a precise shot, all he would need to do is adjust his sight and suddenly he could be striking dead-center. However, if such a marksman was accurate but imprecise, it may mean that the average position of his shots were close to the center, but scattered like a random distribution across a particular area (a much more difficult problem to address).

Now, the majority of your responses appear accurate ;) but the first question sounds to be more a matter of semantics. The definitions themselves I have just described for you do not change based upon measurement, but the specific qualities of "being accurate/inaccurate" and or "being precise/imprecise" can and do change.

  1. What it means to be accurate/precise

VS.

  1. What is considered to be accurate/precise in a given context

If I were you, I would ask my instructor to clarify between these two possibilities, but make certain you show that you understand the distinction between the two terms.

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