Accurate, precise, both, or neither?

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AI Thread Summary
The discussion centers on the accuracy and precision of three density measurements of water, which are 1.9141, 1.9584, and 1.8991, compared to the actual value of 1.9583. The consensus is that the measurements are neither precise nor accurate, as they vary significantly and do not closely align with the true value. The calculated mean of the measurements is 1.9239, which is approximately 0.03 away from the actual value, raising questions about its accuracy depending on the required precision standard. The conversation emphasizes that definitions of accuracy and precision can vary based on specific criteria, such as the number of decimal places needed. Ultimately, the conclusion is that the measurements do not meet the necessary standards for either accuracy or precision.
Lori

Homework Statement


1.9584 is the measured density of water...

student measures 3 trials:
1. 1.9141
2. 1.9584
3.1.8991

Homework Equations


Precise - the closeness of the measurements to each other
accuracy- the closenses of measures to the actual value

The Attempt at a Solution


I'm thinking it's neither precise or accurate. The values are not close to 1.9583, they differ quite different given that the actual measured values have more decimal places.

Also, it wouldn't be precise because they all different greater than 0.01
 
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Lori said:
Also, it wouldn't be precise because they all different greater than 0.01
Depends on your standards, but a 0.5% precision shouldn't be too hard, yes.
Lori said:
The values are not close to 1.9583, they differ quite different given that the actual measured values have more decimal places.
What is their mean? How much does that differ from the precise value, if you consider the spread of the measurements?
 
mfb said:
Depends on your standards, but a 0.5% precision shouldn't be too hard, yes.What is their mean? How much does that differ from the precise value, if you consider the spread of the measurements?
the mean is 1.9239 which is like 0.03 away from the actual measurement. Would this make it accurate?
 
It is not sufficient to tell if many measurements would have the right average or not.
 
Lori said:
the mean is 1.9239 which is like 0.03 away from the actual measurement. Would this make it accurate?
Define "accurate" !

If the specification is that you need accuracy to two decimal places, then yes. If you need it to 8 decimal places, then no.
 
Just as an aside, and not because I think you don't understand the difference between precision and accuracy, this is how I was taught to remember the difference.

How do you get from Washington DC to the middle of Texas?
Precise answer: <long set of very detailed directions that ends you up somewhere near Boston.>
Accurate answer: Go to Oklahoma and turn left.​
 
mfb said:
It is not sufficient to tell if many measurements would have the right average or not.
I wasnt sure of the answer because it was multiple choice. So, i just picked neither precise or accurate
 

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