Sample Exercise In a counting exercise where the average number of counts expected from background is 3, what should the minimum alarm set point be to produce a false alarm probability of 0.001 or less?
Is a Density Function, or cumulative probability (as opposed to discreet). Can use look-up table or Excel functions to apply Scale to data by use of Mean and Standard Deviation Single-sided confidence – but can be used to determine two-sided confidence function “Erf(x)”.
Controlling False Alarm Probability Determine expected number of background counts that would occur in a single count cycle. Determine the StdDev of that value Set the alarm setpoint a sufficient number of Standard Deviations above average background counts for an acceptable false alarm probability.
“Minimum” Count Time Solve for T using the simplified equation below, and round up to a full no. of seconds: Compute a new value for MDA (see next slide) using the resulting “T” as As needed, iteratively, add 1 second to the T and recompute MDA until the result is < the desired MDA
Computing MDA Start with MDA=1 for the right side of the following equation, and compute a new value for MDA Substitute the new value on the right hand side and repeat. Continue with the substitution/computation until the value for MDA is sufficiently close to the previous value.