Say i have two different uncertainties of different units. Say one is of measurement (metres) and one is of frequency. How do I combine these to get a total uncertainty which has both in them??
Any help would be appreciated.
Thanks


I need a bit of help...quick please!
Started by AM4R, Apr 21 2007 09:56 AM
6 replies to this topic
#1
Posted 21 April 2007 - 09:56 AM
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#2
Posted 21 April 2007 - 12:48 PM
You have to combine them as percentage uncertainties.
HMFC - Founded 1874, beefing the Cabbage since 1875
#3
Posted 21 April 2007 - 09:49 PM
any idea how i do that?
Thanks
Thanks
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#4
Posted 22 April 2007 - 12:21 PM
any idea how i do that?
Thanks
To get the uncertainties as percentage uncertainties, you need to express the uncertainty as a percentage of what you were measuring. For example, say you were measuring the length of something, and it came out to be 40cm, and there was a scale reading uncertainty of Thanks



You would get your other uncertainty(or ies) in terms of a percentage in that quantity, and then you can combine them in the normal way.
HMFC - Founded 1874, beefing the Cabbage since 1875
#5
Posted 22 April 2007 - 01:19 PM
What is the normal way?
I was wondering for my chem invest and just ended up adding them.
I was wondering for my chem invest and just ended up adding them.
#7
Posted 22 April 2007 - 04:52 PM
I was hoping that wouldn't come up
I can't remember how it was done in higher physics, but adding is probably fine. At physics advanced higher you would get everything as percentage errors, square them, add them together and then take the square root. So if your percentage errors were a,b and c, then your total percentage error P would be
(however, if any errors are less than a third of your largest error you would disregard them). That's not part of the chemistry course though, so I don't think they would expect you to use that.


HMFC - Founded 1874, beefing the Cabbage since 1875
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