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From: sgb@mulga.OZ (Steven Bird)
Newsgroups: net.math
Subject: Re: The Perils of Nutrasweet: digits of precision
Message-ID: <866@mulga.OZ>
Date: Mon, 19-Aug-85 02:54:26 EDT
Article-I.D.: mulga.866
Posted: Mon Aug 19 02:54:26 1985
Date-Received: Sun, 25-Aug-85 13:54:02 EDT
References: <771@burl.UUCP> <394@petrus.UUCP> <182@steinmetz.UUCP>
Reply-To: sgb@mulga.OZ (Steven Bird)
Organization: Comp Sci, Melbourne Uni, Australia
Lines: 23

> 	This is getting rather off the point, but some of you might like
> this.  During one of my interviews for college, I was asked a typical
> stupid interview question: "What's the area of a table 3 meters wide by 4
> meters long?"  I poked around with various counter-probes like, "Do you
> mean the area of just the top surface, or the top and bottom combined?" and
> then came up with the obvious answer; 12 meters^2.

> 	Anyway, it turns out the "correct" answer is 1 * 10^1 meters^2;
> since the initial data only had 1 digit of accuracy, that's all the final
> answer can have.

Getting even more off the point, suppose we were to compute 3*4 in base 12.
The answer of course is 10(base 12) which has 1 significant figure as required.
10(base 12) translates to 12 +/- 6 (base 10) which I think is more acceptable
than the 10 +/- 5 implied by 1 * 10^1 metres^2 above.

Error analysis should be *independent* of the base used to represent numbers.
For this reason I think there is something fundamentally wrong with the use
of significant figures to express accuracy.

-- 
Steven Bird.                        PHONE: +613 344-5229  (03 344-5229)
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