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Re: [Phys-l] formatting uncertainties



If a number used to calculate that ratio comes from an experimental measurement, there definitely is uncertainty whether it's stated as +- or not. The uncertainty would be in the "4". However, if you arrive at that ratio from the conversion factor for inches <--> cm, it's an exact ratio. The inch is defined as exactly 2.54 cm.

Context is important.

BN
Union University

John Denker <jsd@av8n.com> 1/24/2008 5:34 pm >>>
On 01/24/2008 12:17 PM, Robert Cohen wrote:
<snip>
Suppose the ratio of two things comes out to be 2.54.
Do you know the uncertainty of that number, even vaguely?

Hint: That number might be the number of cm in an inch.
Or not.
<snip>