NIST standards

Main Entry: pre·cise
Pronunciation: pri-'sIs
Function: adjective
Etymology: Middle English, from Middle French precis, from Latin praecisus, past participle of praecidere to cut off, from prae- + caedere to cut
1 : exactly or sharply defined or stated
2 : minutely exact
3 : strictly conforming to a pattern, standard, or convention
4 : distinguished from every other <at just that precise moment>

Main Entry: ac·cu·rate
Pronunciation: 'a-ky&-r&t, 'a-k(&-)r&t
Function: adjective
Etymology: Latin accuratus, from past participle of accurare to take care of, from ad- + cura care
1 : free from error especially as the result of care <an accurate diagnosis>
2 : conforming exactly to truth or to a standard : EXACT <providing accurate color>
3 : able to give an accurate result <an accurate gauge>

Does that help?

Precision is the repeatability of an instrument in taking a measurement. If the scatter of measuring the same parameter is small, then the precision is good. If the scatter is large, then the precision is bad.

Accuracy is how close a measurement is to the real world. If an instrument always gives a value which is too large, then it is inaccurate by that amount.

Refer to Wikipedia's defiinition of accuracy and precision. It contains some good visual aids.

GWJ is on the mark.

I am thinking you are not a native English speaker. Same as me, I speak Texan.

When dealing with industry standards and specifications, great lengths are gone to in an effort to eliminate gray areas. More specifically to remove the concept and liability of interpretation from the procedure or method.

An example would be, a statement of definition in a spec that clarifies the difference of meanings between 'should' and 'shall'. Similar, but not the same. Yet different enough that elaboration is needed to remove the interprative possibilities.

I commend you on realizing that there is a difference and that the difference is noteworthy

cr3

The following is quoted directly from the "CCT Primer by Phillip Stien", published by the Quality Council of Indiana 2003.

"Accuracy is the lack of bias between the user's current measurement process and the same process using an accepted standard as a reference. ISO VIM (1993) defines accuracy of measurement as the "closeness of the agreement between the result of a measurement and a true value of the measureand".

"Precision describes how close in value successive measurement results fall when attempting to repeat the same measurement. This variabilty is often well described by random distribution, such as the Gaussian or Normal. Precision may be quantified using a statistical measure of spread such as the standard deviation and is usually visualized as varying rapidly so that successive measurements will experience all aspects of the distribution."