https:

## Message Posted: Thu, 16 May 2002 @ 18:11:17 GMT

 < Last>>

 Subj: Re: Rounding in Teradata From: Buckland

Teradata follows the IEEE standard for rounding, which is exactly what you laid out. If the number next to the 5 is even it rounds down. If it is odd it rounds up. Or restating "the 5 rounds to the closest even number".

Here's the reason for that -- It keeps the sum from getting a systematic error. Many people think that any '5' should round up (or down). If anything that ends in 5 rounds up then the sum of a large list will have a slight upward bias. Essentially 1,2,3,4 would round down and 5,6,7,8,9 would round up (numbers ending in 0 don't round). So the sum of large column of these rounded numbers would likely be slightly larger than the actual sum of the non rounded numbers.

By dividing the numbers ending in 5 (half up, half down) the errors introduced by rounding cancel themselves out. Therefore a large sum of these numbers won't have an upward (or downward) bias. If you change how things round be sure that a slight upward bias of the rounded numbers isn't important.

Mike Buckland

 < Last>>

Attachments

Library

Quick Reference

Archives

Sample Index

 2016 2007 2015 2006 2014 2005 2013 2004 2012 2003 2011 2002 2010 2001 2009 2000 2008 1999

2002 Indexes

 Jan Jul Feb Aug Mar Sep Apr Oct May Nov Jun Dec

 Top Home Privacy Feedback