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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.

Thanks,

Ben

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# Homework Help: Errors on decay constants

Can you offer guidance or do you also need help?

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