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: Errors on decay constants

  1. Apr 1, 2005 #1

    I am trying to determine the half lives of two radioisotopes in a neutron activated sample of copper. I have plotted the the ln(activity) vs. time and then used the linest function on excel to get a decay function for the longer half-life by assuming after a certain time, only the longer halflife isotope would contribute. This was then subtracted from the total activity and thus a value for the shorter halflife component could be determined through the linest function again. A minimum chi squared value was found through 'solver' on excel by altering the constants in this fitted function. Because I am fitting a hypothesis to data each chi squared component will be (observed count rate - fitted function rate)^2/fitted function rate. This then produced the best possible function to fit the data. The problem with determining the error on this function is: how does the poisson error of +-sqrt(N) on each data point affect the error on the fitted function?
    I have tried settin the minimum chi squared to +1 its original value but this gives very small error values as might be expected...

    Any help on this could well save my life.

  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted