1. Not finding help here? Sign up for a free 30min 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!

Errors problem

  1. Nov 10, 2004 #1
    Hi im currently trying to write up a lab report for my 3rd year lab on the scintillation counter and im struggling to convert the error i have for the gradient and intercept (using polyfit on excel) and the uncertainty i have in my x values, to the uncertainty in my energy measurements where energy=mx+c. c is the y intercept and m the gradient. The x value here is the channel number for the photo peak with an error of plus or minus 2, My gradient is 0.0037 with error 0.0002 and intercept -0.0187 with error 0.005. How do i get the error in energy from this, note the uncertainty in channel number was always 2 despite it ranging from 40 to 400. any help would be much appreciated.
     
  2. jcsd
  3. Nov 11, 2004 #2
    Any hints?
     
  4. Nov 11, 2004 #3
    Uncertainty for a general function f(a,b,c) can be calculated from

    [tex] \sigma_f^2 = \left( \frac{\partial f}{\partial a}\right)^2{\sigma_a}^2 + \left( \frac{\partial f}{\partial b}\right)^2{\sigma_b}^2 + \left( \frac{\partial f}{\partial c} \right)^2{\sigma_c}^2[/tex]

    It's easy to see how this equation would extend to a function of more variables.

    --J
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Errors problem
Loading...