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Homework Help: Errors/Data Analysis

  1. Feb 2, 2012 #1
    Hi there,

    I have a pretty basic question on error analysis. say we want to obtain a quantity which is given by u+v.

    if u = 8.5452545 and has uncert 0.025454. it would be quoted as 8.55(2) and if v = 3.865898 and has uncert 0.04124343.

    it would be quoted as 3.87(4).

    but when calculating say u+v....

    do i a) use 8.55 and 3.87 and their rounded uncertainties.

    or b) use the raw data?

    thanks for any help.
  2. jcsd
  3. Feb 2, 2012 #2
    The uncertainty of a given value must be in the last significant figure.
    So if u is given as 8.5452545 the uncertainty is in the last figure 0f 5.
    It means that u lies between 8.5452544 and u = 8.5452546.
    This is what is meant by SIGNIFICANT figures.
    Hope this helps
  4. Feb 2, 2012 #3
    no sorry it doesn't help.

    I'm not sure when calculating a new value experimentally if I use the rounded values or the raw values of the old data?

    I know what sig figs mean.
  5. Feb 2, 2012 #4
    where did these figures come from?
    Are they from a question you have seen?
    Were they given to you to test your understanding?
    Are they values you have measured?
  6. Feb 2, 2012 #5
    The values are made up. I am writing up a report and wasn't sure what to do.
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