Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site aoa.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!gamma!epsilon!zeta!sabre!petrus!bellcore!decvax!genrad!panda!talcott!harvard!bbnccv!bbncca!aoa!carl
From: carl@aoa.UUCP (Carl Witthoft)
Newsgroups: net.math
Subject: Re: significant digits
Message-ID: <284@aoa.UUCP>
Date: Thu, 5-Sep-85 08:10:35 EDT
Article-I.D.: aoa.284
Posted: Thu Sep  5 08:10:35 1985
Date-Received: Sat, 7-Sep-85 05:27:06 EDT
References: <2244@utcsstat.UUCP> <382@rti-sel.UUCP> <681@tpvax.fluke.UUCP>
Reply-To: carl@aoa.UUCP (Carl Witthoft)
Organization: Adaptive Optics Assoc., Cambridge, Mass. USA
Lines: 33

In article <681@tpvax.fluke.UUCP> inc@fluke.UUCP (Gary Benson) writes:
>> If I tell you that a right triangle has sides of length 3 and 4
>> and ask you for the length of the hypotenuse are you going
>> to answer '5' or are you going to worry about errors in measurement?
>> If I ask you 'What is 6+7' are you going to answer 1x10^1??
>> then I am wrong and proud of it.
>> 	Tom Truscott
>
>Thanks for a breath of fresh air, Tom. It seems so droll and esoteric to
>insist that the table exists in some realm of thought unaffected by first
>rules. Your examples were all to the point, and nicely refute the eggheads'
>stubborn stance. It's those who argue the obverse who give science it's
reputation for stogginess and indirection.
x
x
Before this stuff goes off any further, let me point out two things:
1) There's a big difference between the mathematical 3 and the scientific
measurement 3 . Thus the stuff about triangles is irrelevant.
2) There's more to life than sig figs. While it is roughly true that
a properly reported measurement of 3m by 4m does imply an error of 
+/-.5m on each measurement, it is NOT true that the  result of any computation
is allowed only *one sig fig*. The allowed error depends on the precision,i.e.
percent uncertainty, of the inputs and on the computation done. 
It should be clear that the percent errors in "s=1m" and "s=8m" are
different. 



        Darwin's Dad (Carl Witthoft)
	...!{decvax,linus,ima,ihnp4}!bbncca!aoa!carl
	@ Adaptive Optics Assoc., 54 Cambridgepark Dr.
	Cambridge, MA 02140	617-864-0201
" Buffet-Crampon R-13 , VanDoren B-45, and VanDoren Fortes ."