Re: Chi Squared Test

[William V Lipton <liptonw@dteenergy.com>]

At Fermi 2, we require 15 sequential source counts when setting up a quality
control chart for a laboratory instrument.  The count time must be
sufficient to generate at least 40,000 counts.  The results are used to
calculate a chi square value, which is the ratio of the observed variance to
the theoretical variance based on Poisson statistics.  The upper and lower
acceptable limits for this value are the 0.975 and 0.025 probability values
for chi square, which, for 15 counts, would be 26.1 and 5.63.   Please
e-mail me if you have any questions on this.

The opinions expressed are strictly mine.
It's not about dose, it's about trust.

Bill Lipton
liptonw@dteenergy.com

Joel Cehn wrote:

> We use the chi-squared test on 10 sequential readings to check the
> stability of a wipe counter (Ludlum 2929.)  What do people consider
> acceptable results from this test?
>
> Joel Cehn, CHP
> JCehn@att.net
>
> ***********

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