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- Path: sparky!uunet!usc!usc!not-for-mail
- From: bruck@mtha.usc.edu (Ronald Bruck)
- Newsgroups: sci.math
- Subject: Re: Rounding Rules
- Date: 20 Dec 1992 08:06:55 -0800
- Organization: University of Southern California, Los Angeles, CA
- Lines: 25
- Message-ID: <1h25mvINN1gl@mtha.usc.edu>
- References: <1992Dec20.003018.14325@sol.ctr.columbia.edu>
- NNTP-Posting-Host: mtha.usc.edu
-
- In article <1992Dec20.003018.14325@sol.ctr.columbia.edu> shaw@toadflax.UCDavis.EDU (Rob Shaw) writes:
- >
- >What is the rationale behind the following rounding rule?
- >
- >when dealing with 5's followed by all zero's, check the
- >next digit to the left. If it's even, round down; odd,
- >round up.
- >
- >For example both 1.13500 and 1.14500 are 1.14 to 3 places.
- >What is the advantage of having the interval closed at both
- >ends around even digits, and open at both ends around odds?
- >
-
- The purpose is to make addition more accurate. Assuming there
- is no systematic error, i.e. in half the cases the 5 is preceded
- by an even and in half the cases by an odd, then this rule will
- cancel the errors. "Round to even" sounds as if it discriminates
- against odds, but if you add 10^9 terms following some other
- rule, your purported sum may be way off.
-
- --Ron Bruck
- bruck@mtha.usc.edu preferred
-
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