Is a "shift in the meaning" of Accuracy and Precision occurring? Accuracy and precision are among the most fundamental concepts in experimental physics, and, I always believed, completely unambiguous.
Recently I found that the Wikipedia article on Accuracy and Precision claims that a "shift in the meaning of these terms" is occurring. My first thought was that this must be a joke, a mistake or Wiki vandalism.
However, the ISO 5725-1 (Accuracy (trueness and precision) of measurement methods and results) standard referenced in the article indeed reads

3.7accuracy
[...]
NOTE 3 Accuracy refers to a combination of trueness and precision.

Notably, this seems to imply that the concept of precision is a subset of the concept of accuracy, which is plainly incompatible with the definitions found almost everywhere else that sharply contrast precision and accuracy.

My questions are:


*

*Is such a "shift in meaning" really occurring in the physics/measurement community at large?

*If yes, what is the cause of this change of terminology?

 A: The "shift in the meaning" refers to some attempts to reinterpret the terminology that were made by a metrological document, ISO 5725, in 2008. That may be described as a bureaucratic effort by a few officials – really bureaucrats of a sort – and as far as I know, the "shift in the meaning" hasn't penetrated to the community of professionals. The people behind the standards have certain limited tools to assure that their new interpretation of the words would be taught to students of physics and engineering but I don't think that they are succeeding so far.
Before 2008, people would agree that "precision" refers to the typical difference between individual measurements, and the precision is good if a "statistical error" is low or if the measurements are producing "many significant figures" for the result.
"Precision" didn't – and still doesn't – discuss whether the results of the measurements are actually clustered around the true value. They may be separated by a "systematic error" – which goes in the same direction in each repetition of the measurement and can't be removed by averaging many measurements. The absence (or low magnitude) of this "true" systematic error – the difference between the true value and the average of many measurements – would be summarized by the word "accuracy".
One wants results that are both "precise" and "accurate" in the sense above, and a word like "valid" or "satisfactory" or another similarly neutral non-technical word would be reserved for results that are both "precise" and "accurate".
The "shifted" 2008 proposal is to use the word "accurate" for what would previously be called "valid" etc. – i.e. for measurements that suppress both kinds of errors, systematic and statistical, i.e. for measurements that are both accurate (in the pre-2008 sense) and precise (in the pre-2008 sense which is the same as post-2008 sense).
Even if this "shift" succeeded in the language of professionals, it won't make much difference. The reason is that the word "accurate" has pretty much implicitly included "precise" even before 2008. If you make a small number of measurements (repetitions of a measurement) and you want to determine whether the measurements are "accurate", you have to calculate the difference between the true value and the measured values. But if you have just one or several measured values, the difference is affected by the "statistical error", anyway, so you can't quantify the "systematic error" well, anyway. To be sure that the systematic error is low, after just a few measurements, the statistical error has to be low, too (the precision has to be good).
So whether the word "accuracy" included "precision" before 2008 is debatable. All these things are just changes at the level of the language. When one is quantitative, things have to be described by actual quantities – systematic errors and statistical errors and nothing was changed about the meaning of these quantities in the 2008 document.
A: (Currently editing answer.. previous version at https://physics.stackexchange.com/revisions/135002/7)
A: I'm not familiar with ISO 5725 (a 1994 revision of a 1986 document, apparently "reviewed and confirmed" in 2012), and it seems that I have to buy it to read it. A 2008 vocabulary of metrology put out by the BIPM and also cited by Wikipedia has definitions much closer to my intuition, and to common usage among folks I know who specialize in precision measurements:

2.13(3.5)
measurement accuracy
  accuracy of measurement
  accuracy   
closeness of agreement between a
  measured quantity value and a
  true quantity value of a
  measurand 
…
NOTE 2 The term “measurement accuracy” should not be used for
  measurement trueness and the term measurement precision should not be
  used for ‘measurement accuracy’, which, however, is related to both
  these concepts.
…
2.14
measurement trueness
  trueness of measurement
  trueness  
closeness of agreement between the average of an
  infinite number of replicate
  measured quantity
  values
  and a
  reference quantity value
…
NOTE 3
  Measurement accuracy
  should not be used for
  ‘measurement trueness’ and vice versa. 
…
2.15
measurement precision
  precision
  closeness of agreement between
  indications
  or
  measured quantity values
  obtained by replicate
  measurements
  on the same or similar objects
  under specified conditions
…
NOTE 4 Sometimes “measurement precision” is erroneously used to mean
  measurement accuracy. 

However, it's worth remembering that in the extreme of terrible precision, so many measurements may be needed to determine whether the average is accurate or not that the measurements may be effectively useless. Remember the old joke about the three economists playing darts at the pub: the first puts his darts in the wall above the dartboard, the second puts his darts in the wall below the dartboard, and third gets excited and yells "Bullseye!"
