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First try didn't fly.  I've attached a jpg at the bottom.

The picture didn't paste in, so I've attached it.
Just in case anybody missed it, I took a picture of Paul's data.
There's a seasonal periodicity and the watch and clock are in
opposite phase!

Fred


Overlay Plot



On Jan 11, 2009, at 12:18 PM, Paul Hirose wrote:

>
> It may be interesting to look at the seasonal variations in daily rate
> of an ordinary battery powered wall clock. I check this clock monthly,
> so the values are the average daily rate for the month. All values are
> positive, i.e., the clock always runs fast.
>
>       2006  2007  2008
> Jan   .40   .38*  .37
> Feb   .40   .45   .39
> Mar   .38   .46   .44
> Apr   .43   .46   .45
> May   .47   .50   .50
> Jun   .48   .52   .52*
> Jul   .40   .48   .50
> Aug   .48   .48   .49
> Sep   .47   .50   .52
> Oct   .44   .47   .49
> Nov   .41   .41   .46
> Dec   .35   .38   .41
>
> * new battery installed at beginning of this month
>
>
> And here are values for a $25 Timex digital watch I bought in 2000. It
> still has the original battery. I don't wear this watch a lot;
> probably
> less than 5 hours per week.
>
>       2006  2007  2008
> Jan   .43   .41   .42
> Feb   .40   .42   .42
> Mar   .41   .43   .45
> Apr   .41   .41   .43
> May   .39   .41   .42
> Jun   .34   .40   .38
> Jul   .26   .35   .34
> Aug   .35   .34   .34
> Sep   .40   .40   .40
> Oct   .43   .45   .43
> Nov   .43   .44   .46
> Dec   .41   .43   .44
>
>
> The time checks are by eye and ear using WWV on a cell phone. By
> comparing the phone audio to the audio from a shortwave receiver I've
> found that the phone is consistently 1/4 second late, as well as I can
> estimate, so this constant is disregarded.
>
> My monthly error checks are accurate to perhaps 1/4 second, so the
> corresponding daily rate is probably accurate to plus or minus .01
> second.
>
> --
> I block messages that contain attachments or HTML.


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