1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Simple question about Error Analysis

  1. Feb 17, 2013 #1
    I'm doing a report on a set of lab data and am supposed to find the mean and mean's standard deviation

    [tex] \bar{x} + \sigma_{\bar{x}} [/tex]

    The mean is given by

    [tex]\displaystyle{ \bar{x} = \sum_{i=1}^{N} w_{i} x_{i} } [/tex]

    Where

    [tex]\displaystyle{ w_{i} = \left( \frac{\sigma}{\sigma_{i}} \right)^2 } [/tex]

    and for the error (mean's standard deviation)

    [tex] \displaystyle{ \sigma_{\bar{x}} = \sigma = \frac{1}{ \sqrt{ \sum_{i=1}^{N} \frac{1}{\sigma_{i}^{2} } } } } [/tex]


    The problem is I can't quite figure it out what the σi would be, is it the standard deviation? This might sound very silly but it's been a long time I've dealt with this.

    Any help is appreciated.
     
  2. jcsd
  3. Feb 17, 2013 #2

    mfb

    User Avatar
    2017 Award

    Staff: Mentor

    σi is the uncertainty (standard deviation*) of data point i.

    *any multiple of it will work as well, if you keep it consistent, as it cancels in the fraction
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...