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Re: Efficiency plot using AIDA [message #1548 is a reply to message #1510] 
Fri, 11 July 2008 11:51 
partridge Messages: 11 Registered: October 2005 



Hi Tony,
It looks like the code from Adam is calculating 95% CL intervals instead of 1 sigma error bars. That probably explains why the errors were a factor of ~2 too big compared to my estimates using binomial errors.
When there are more than 10 entries, this is explicit, as shown from the code fragment from EfficiencyBinError shown below:
69: if (NX >= 10) {
70: // NUMBERS ARE ALL LARGE, SO CAN USE ANALYTIC CALCULATION
71: return 1.96*Math.sqrt(R1*(R2R1)/R2)/R2;
72: }
What is being returned is just a factor of 1.96 times the binomial error.
I personally don't think 95% CL errors are all that useful  when people look at a plot they are expecting 68% CL errors unless there is a good reason for doing something different.
I also am not sure exactly what Adam was doing for the case of less than 10 entries  it looked like there were a bunch of special cases and it is hard to tell by looking at the code if they make sense.
I would be happy to code a version of EfficiencyBinError that simply returned binomial errors if that would be useful.



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