Expert: Ahmed Salami - 9/19/2004

Question
How can you figure out what is good precision and accuracy? I asked my teacher and he explained to me how to do the percent error. What I forgot to ask him was how do you know from the percent of error if something is accurate or precise or both. I have a test coming up in 2 days and won't see him till then so if you could help me, it would be a great help. Have a good day.

Answer
Hi Jeff,
Like i mentioned before, accuracy is measured in terms of absolute error and that is where percentage error comes in.
So, obviously the percent error would only tell you how accurate a particular measurement is. Remember that you can only talk about the accuracy of a particular measurement, precision on the other hand deals with the agreement between a set of measurements.
However, if you would like to know how precise a set of measurements is by using percent errors, all you have to do is find the percent error for each measurement and see how close they are.
I wish you good luck.
Regards.