[QUANTITY] Why quantities always have errors (Was: Re: [QUANTIT] Use-cases, role in larger scheme)

[Brian Thomas]

On Monday 17 November 2003 11:21 am, DIDELON Pierre wrote:
> Why trying to forbidd the concept of number without error
> if it can be introduce (for free) and claim as necessary by some people?

	I for one believe it is "an error" to have a number without an error. 
	You have to ask yourself, what does it mean when the error is not present? 
	There are at least 2 possibilities: the number is "exact" -or- it may mean that 
	we "don't know" the error because the publisher of the number was "lazy" 
	(yes, this does happen. Many journal articles, for example, have papers with 
	columns of numbers and no errors in them but should have them). 

	Treatment of these types of "errorless" numbers  is presumeably different,
	if you want to do a calculation with them. In the first case, error propagation	
	is straitforward and clear. In the second case, the user may choose to
	either do a "sloppy" calculation, noting the problem in the errors, -or-
	do no calculation at all.

	Hence, I believe, statements about errors are *always* appropriate, even if
	they aren't present.

	Regards,

	=b.t.

-- 

  * Dr. Brian Thomas 

  * Code 630.1 
  * Goddard Space Flight Center NASA

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