On 10/27/20 6:16 PM, Tom Van Baak wrote:
Alberto,
Thanks for asking. The correct spelling is Allan variance or Allan
deviation, named after David Allan, of NBS (NIST). Yes, on rare
occasions it is misspelled Allen, as in the hex key wrench. Note it's
spelled correctly in the Subject line of this thread. I'm not aware of
national explanations for the misspelling; it could simply be that allen
is more popular a name than allan and a spell checker allows either one.
The ADEV statistic itself is spelled Allan because that's his name: Dr.
David W. Allan. Similarly, the hex wrench is spelled Allen because of
Mr. William G. Allen.
More fun: When you google word search it displays a hit count:
"allan deviation" About 84,300 results (0.46 seconds)
"allen deviation" About 2,460 results (0.40 seconds)
"allan variance" About 85,400 results (0.41 seconds)
"allen variance" About 21,300 results (0.37 seconds)
"allen wrench" About 4,820,000 results (0.52 seconds)
"allan" About 213,000,000 results (0.77 seconds)
"allen" About 1,190,000,000 results (0.87 seconds)
You can see that the word allen is 5x more popular than allan. That
alone may explain the occasion misspelling of ADEV. Also, apparently,
Allen wrench tools are 50x more popular than Allan deviation tools ;-)
I'm still agitating for alien deviation - Microsoft offers it as a
suggestion, but not Allan, so it must be true.
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