Magnus is quite right. Variance is almost always just a value on its way to becoming another value. Squared units make little sense in most applications.
Bill (the statistician) On Mon, Mar 28, 2011 at 1:10 PM, Magnus Danielson < [email protected]> wrote: > On 03/28/2011 02:36 PM, Bruce Griffiths wrote: > >> Martyn Smith wrote: >> >>> Hello, >>> >>> I'm trying to compare the stability specifications of two oscillators. >>> >>> The first spec is 2 x 10E-11 Allan Variance. >>> The second spec is 3 x 10E-11 Allan Deviation. >>> >>> As Allan deviation (ADEV), is the square root of Allan variance, I >>> thought the first spec is the better of the two, but a collegue >>> disagrees, saying 3x10E-11 Allan Deviation is a better spec than 2 x >>> 10E-11 Allan Variance. >>> >>> I'm sure the million experts at there will give me the correct answer >>> >>> Regards >>> >>> Steve Jones >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> Strictly you are correct, however some early datasheets (eg Crystek, ) >> say Allan variance whilst they actually tabulated its square root or >> Allan deviation. >> > > It's also common to have plots saying "Allan Variance" and plotting the > Allan Deviation. > > Since Allan Deviation is the square root of Allan Variance, 2E-11 Allan > Variance is about 4.5E-6 in Allan Deviation so an Allan Deviation of 3E-11 > is better than an Allan Variance of 2E-11... by far. > > Use Allan Deviation through-out. > > Cheers, > Magnus > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
