When someone says for example "We measured it to within 3%" Does this mean 3% is the percentage error?

Question

astrophysics · Answer

Depends...most of the time they would clarify whether or not it's error or what ever you're measuring. Is there more to this?

astrophysics · Answer

A lot of the times it's the error

unklerhaukus · Answer

Often we perform measurements of quantities that we do not know the exact value of.
Measurement techniques are not infinitely precise. 

If a measurement determines the value a quantity to to be 100±3, then the relative percentage error in the measurement is 3%.

This mean that the true value is determined to be somewhere between 97 and 103.
The true value could be 100, in which case the percentage error is actually 0%. 

But the true value could also be 103. In which case the actual percentage error is 3%.

From the measurement, the percentage error of the measured value can only be know to be less than or equal to 3%.

isaiah.feynman · Answer

No more. I listen to scientists talk. I hear them say for example we measured it to within 2%. I wonder if this "2%" just means percentage error. For example if the true mass of something is 5g and I measured it to be 4.7g, after calculating the percentage error which is 6%, can I say that I measured the mass to within 6%?

astrophysics · Answer

Ah gotcha, so yes in physics we say that it's $$\pm 0.03$$ within the error, or percent, but percentage is often used in chem rather than physics hehe

astrophysics · Answer

Or put 3% depending on the measurement haha

astrophysics · Answer

As someone who's done quite a bit of error measurements/ calculations yup they mean $$\pm 3 \%$$