bootstrap methodsrotondi/bootstrap.pdf · 21 the dual bootstrap fix the background on one sample...

Bootstrap Methods

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The best one !!!

The non parametricSampling methods

Up to 2006

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Non parametric Bootstrap

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Bootstrap of B1 and Bi data

Trimmed mean 50%Correlation between measurementsWeighted resampling Int(1/s2) timesThe error on measurements is not considered

Scope of the analysis: to test wether errors only or the data itself are unreliable

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Results

Bootstrap:

Standard analysis:

1.36.03.1

3.818.85

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9.33.05.1

6.806.86

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Some data areunreliable

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Useful when the two samples are signal and background....

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The dual Bootstrap

Fix the background on one sample and calculated the peak signalwith another sample to avoid biases !!

Repeat on bootstrap samples (dual bootstrap)

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A word on the permutation tests

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Conclusions•Poissonian Counting: most of the tests do not consider the error on background andoverestimate the signal. Often true (mean) valuesand measured values are improperly confused.

•Binomial counting: a general theory there existsand should be applied.

•The errors should be calculated by MC methodsand the procedure checked with MC toy models

•Nonparametric Bootstrap methods should be usedalso by physicists