Accurate, precise, both, or neither?

[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

 

[mfb]

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.

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?

 

[Lori]

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?

 

[mfb]

It is not sufficient to tell if many measurements would have the right average or not.

 

[phinds]

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.

 

[phinds]

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.​

 

[Lori]

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