Measuring accuracy

[bmb15]

I come back to the OP's initial question "....on determining accuracy--- the +2/-2 Spd is supposed to be an average over what time frame"

In my view this thread has not yet given a clear answer; the question shows a fundamental misinterpretation of the +/- 2 seconds per day (Spd or s/d) published by Rolex.

I don't know any document where Rolex guarantees the ACCURACY of their modern watches. The reason why is absolutely clear: ACCURACY can strongly depend on wearing pattern and many other factors, as already explained quite often in this forum.

Instead, Rolex guarantees a PRECISION of +/- 2 s/d. The difference between ACCURACY and PRECISION I explained here in post # 29, and at several places in literature.

All measurement results presented in this thread are ACCURACY measurements, which need a reference time to compare with, e.g. an atomic watch to which an app refers.

Therefore, all these data are not comparable with the +/- 2s/d PRECISION guaranteed by Rolex.

To determine the PRECISION you need to do many (>> 2-3) measurements, then analyse the results, determine the average value and its standard deviation.

In other words, the spread of the measured values (standard deviation) is called PRECISION. This is completely independent of the ACCURACY!

One can have all combinations of ACCURACY and PRECISION, as sketched below.



PS: I do not claim the need of super high accuracy Rolex movements! It's just my passion to better understand these calibers and contribute to an interesting discussion. I hope that helps a bit.