Dale,

Actually, I am glad you eventually did sound off - it has been a while on my watch, and by now, SAS-L has been missing your contributions a lot.

Kind regards, ---------------- Paul M. Dorfman Jacksonville, FL ----------------

> -----Original Message----- > From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On > Behalf Of Dale McLerran > Sent: Monday, November 08, 2004 6:42 PM > To: SAS-L@LISTSERV.UGA.EDU > Subject: Re: length of numeric variable > > Ron raises a point which seems quite lost to most people in > todays world. When the slide rule ruled, it was very > important to know just how much accuracy one could assume for a value. > Now, with everything done by computer, many assume that the > statistic spit out is precise to all reported digits. That > is often (usually?) not the case. Ed gives a good > description of what is meant by significant digits. I hope > that folks take heed of the issue of significant digits. > > At the same time that we are discussing significant digits, > let us not forget the other critical element for evaluating a > measure - units of measurement! Remember the mission to Mars > which failed because the engineers on NASA's team were > operating with different measurement units? One can have a > very precise measurement, but if you lose track of the units > of measurement, the precision of the measurement may be of > absolutely no value. > > Thanks for the opportunity to sound off on an issue which has > bothered me much over the past few years. > > Dale > > > --- Ed Heaton <EdHeaton@WESTAT.COM> wrote: > > > Ron; > > > > Significant figures, to an engineer or chemist, are those figures > > which are more than just placeholders. That is, if I aver > that there > > are 300,000,000 people in the US, none of the zeros are > significant; > > they simply move the three over to the left. However, if I > claim that > > there are 100 centimeters in a meter, both of the zeros are > > significant. If I claim that a meter is 39.370 inches, the zero is > > significant. But, if I claim that an inch is > > 0.0254 meters, none of the zeros are significant; they just move the > > 254 > > over to the right. > > > > The scientific community clarifies this problem of > significance with > > scientific notation as follows. > > > > 3*10**8 > > 1.00*10*2 > > 3.9370*10**1 > > 2.54*10**-2 > > > > With scientific notation, all zeros are assumed significant. > > > > The question of significance should only apply to zeros. > If I claim > > that I live 2.97 miles from work, then I either live > between 2.965 and > > 2.975 miles from work or I lie. > > > > Ed > > > > Edward Heaton, SAS Senior Systems Analyst, Westat (An > Employee-Owned > > Research Corporation), 1600 Research Boulevard, RW-3541, > Rockville, MD > > 20850-3195 > > Voice: (301) 610-4818 Fax: (301) 610-5128 > > mailto:EdHeaton@Westat.com http://www.Westat.com > > > > > > -----Original Message----- > > From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On > Behalf Of > > Fehd, Ronald J. > > Sent: Monday, November 08, 2004 3:56 PM > > To: SAS-L@LISTSERV.UGA.EDU > > Subject: Re: length of numeric variable > > > > > > really, people! > > > > are we talking millimeters, miles or megaparsecs? > > > > who remembers > > what the significance of 'significant' digits means ... to an > > engineer? > > > > let me see, iirc: > > "close only counts in horseshoes" > > and Iraq :-Q > > > > Ron > > > > ===== > --------------------------------------- > Dale McLerran > Fred Hutchinson Cancer Research Center > mailto: dmclerra@NO_SPAMfhcrc.org > Ph: (206) 667-2926 > Fax: (206) 667-5977 > --------------------------------------- > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection > around http://mail.yahoo.com >