Virgil's absolutely right. Median as the "middle" value in a _sorted_ set is: - for odd number of data points, it's the middle one: set[N/2] - for even number of data points, it's the average of two in the middle: (set[N/2] + set[(N+1)/2]) / 2
Best regards, Maciej On Tue, Aug 11, 2015 at 3:44 PM, Virgil Griffith <[email protected]> wrote: > I mean the median. > > From Wikipedia... > > For example, if *a* < *b* < *c*, then the median of the list {*a*, *b*, > *c*} is *b*, and, if *a* < *b* < *c* < *d*, then the median of the list { > *a*, *b*, *c*, *d*} is the mean of *b* and *c*; i.e., it is (*b* + *c*) / > 2. > > -V > > On Tue, Aug 11, 2015 at 9:29 PM John <[email protected]> wrote: > >> I think you are confusing the median with the mean: >> >> https://en.wikipedia.org/wiki/Median >> https://en.wikipedia.org/wiki/Mean >> >> Taking the median instead of the mean can be beneficial in situations >> where you have larger outliers in your data, which typically affect the >> mean very much. >> >> -j >> >> Virgil Griffith: >> > Is there some implementation-specific reason not to use the standard >> > mathematical definition of "median"? If not, I propose changing the >> > implementation to become it. >> > >> > -V >> > >> > On Tue, Aug 11, 2015 at 2:44 AM Nick Mathewson <[email protected]> >> wrote: >> > >> >> On Mon, Aug 10, 2015 at 1:11 PM, nusenu <[email protected]> >> wrote: >> >>> -----BEGIN PGP SIGNED MESSAGE----- >> >>> Hash: SHA512 >> >>> >> >>> Hi, >> >>> >> >>> https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n2028 >> >>> >> >>>> If 3 or more authorities provide a Measured= keyword for a router, >> >>>> the authorities produce a consensus containing a "w" Bandwidth= >> >>>> keyword equal to the median of the Measured= votes. >> >>> >> >>> a random sample from recent votes: >> >>> >> >>> grep 37.59.38.117 -A 3 *|grep Measured >> >>> w Bandwidth=6869 Measured=7570 >> >>> w Bandwidth=6869 Measured=15500 >> >>> w Bandwidth=6869 Measured=18100 >> >>> w Bandwidth=6869 Measured=30500 >> >>> >> >>> Tor says the median value is >> >>> 15500 >> >>> >> >>> 2015-08-10-16-00-00-consensus: >> >>> w Bandwidth=15500 >> >>> >> >>> but the median of these 4 values is actually: >> >>> (18100+15500)/2 = 16800 >> >>> no? >> >>> >> >>> Has tor a different definition of 'median' and simply takes always the >> >>> second ordered measurement vote out of 4 votes or is there a bug in >> >>> the spec or implementation? >> >> >> >> There's one misplaced throwaway sentence in dir-spec.txt: >> >> >> >> " All ties in computing medians are broken in favor of the smaller or >> >> earlier item. >> >> " >> >> >> >> We should bring this, and probably other things, into a "definitions" >> >> section earlier in dir-spec.txt. Patches welcome. ;) >> >> >> >> -- >> >> Nick >> >> _______________________________________________ >> >> tor-dev mailing list >> >> [email protected] >> >> https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev >> >> >> > >> > >> > >> > _______________________________________________ >> > tor-dev mailing list >> > [email protected] >> > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev >> > >> _______________________________________________ >> tor-dev mailing list >> [email protected] >> https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev >> > > _______________________________________________ > tor-dev mailing list > [email protected] > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev > >
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