TLimit & nmc

ROOT
1

I’m working on a search with as the performance statistic. My histograms have only 1 bin. The uncertainties are signal stat and bg stat. I send in the statistical error rather than setting stat=true sp that I can scale it for each background.

It seems I need to use 1,000,000 mc to get stable value for . Here are my results for running the exact same code on the same data on a Windows and a linux machine. Notice the doesn’t agree until the run where nmc =1,000,000. http://www.stupidlinux.com/CLs.htm (test points = nmc)

Should I expect this kind of behavior? I expected that I could get away with ~5000 nmc, not 1E6.

2

Could you post a RUNNING script reproducing your problem?
and Please indicate which version of ROOT

Rene

3

Here’s a sample with 1 bin histograms. The results for CLs are dependent on the seed. is not quite as seed dependant.

nmc 10000, seed 0: <CLsb>=0.49842743, <CLb>=0.50030000, <CLs>=0.99625710, CLsb =0.05763818,  CLb =0.06200000,  CLs =0.92964811
nmc 10000, seed 1: <CLsb>=0.49396976, <CLb>=0.50040000, <CLs>=0.98714979, CLsb =0.05556345,  CLb =0.06050000,  CLs =0.91840413
nmc 10000, seed 2: <CLsb>=0.49774903, <CLb>=0.50030000, <CLs>=0.99490111, CLsb =0.06273773,  CLb =0.06560000,  CLs =0.95636780
nmc 10000, seed 3: <CLsb>=0.49959898, <CLb>=0.50020000, <CLs>=0.99879845, CLsb =0.06520442,  CLb =0.06510000,  CLs =1.00160401
nmc 100000, seed 4: <CLsb>=0.49782566, <CLb>=0.50004000, <CLs>=0.99557167, CLsb =0.06005336,  CLb =0.06371000,  CLs =0.94260493
nmc 100000, seed 5: <CLsb>=0.49625125, <CLb>=0.50001000, <CLs>=0.99248265, CLsb =0.05996618,  CLb =0.06309000,  CLs =0.95048632
nmc 100000, seed 6: <CLsb>=0.49848281, <CLb>=0.50001000, <CLs>=0.99694569, CLsb =0.06014540,  CLb =0.06222000,  CLs =0.96665705
nmc 100000, seed 7: <CLsb>=0.49871072, <CLb>=0.50017000, <CLs>=0.99708242, CLsb =0.06110857,  CLb =0.06306000,  CLs =0.96905432
nmc 1000000, seed 8: <CLsb>=0.49852422, <CLb>=0.50024600, <CLs>=0.99655812, CLsb =0.06082244,  CLb =0.06283300,  CLs =0.96800145
nmc 1000000, seed 9: <CLsb>=0.49716198, <CLb>=0.50019900, <CLs>=0.99392838, CLsb =0.06025481,  CLb =0.06336800,  CLs =0.95087127

CLsTest.C (2.54 KB)