[ROOT] Kolmogorow test on weighted histos

From: Andy Salnikov (A.A.Salnikov@inp.nsk.su)
Date: Fri Dec 22 2000 - 07:02:23 MET


Hi all,

it seems that kolmogorov test does not work for me on weighted histograms.
Here is the macro:

{
gROOT->Reset() ;

TH1* h1 = new TH1F("h1","Gauss",200,-5,5);
TH1* h2 = new TH1F("h2","Gauss",200,-5,5);
TH1* h3 = new TH1F("h3","Gauss",200,-5,5);
TH1* h4 = new TH1F("h4","Gauss",200,-5,5);

int j ;
double xs1, xs2 ;

h1->Reset() ;
h2->Reset() ;

for ( j=0; j<10000; ++j ) {
  xs1   = gRandom->Gaus(0,1);
  xs2   = gRandom->Gaus(0,1);
  h1->Fill(xs1);
  h2->Fill(xs2);
}

for ( j = 1 ; j<= 200; ++j ) {
  h3->SetBinContent( j, h1->GetBinContent( j ) / 100 ) ;
  h3->SetBinError( j, h1->GetBinError( j ) / 100 ) ;

  h4->SetBinContent( j, h2->GetBinContent( j ) / 100 ) ;
  h4->SetBinError( j, h2->GetBinError( j ) / 100 ) ;
}

h1->KolmogorovTest(h2,"D") ;
h3->KolmogorovTest(h4,"D") ;

}

And here its output:

 Kolmo Prob  h1 = h1, sum1=10000
 Kolmo Prob  h2 = h2, sum2=10000
 Kolmo Probabil = 0.366721, Max Dist = 0.013
 Kolmo Prob  h1 = h3, sum1=100
 Kolmo Prob  h2 = h4, sum2=100
 Kolmo Probabil = 1, Max Dist = 0.013

I'd expect that probabilities be equal for h1/h2 and h3/h4. What gives?

This was obtained in 2.25/03.

Also probably related question. Should the probability from KolmogorovTest
have flat distibution? When I try call it many times for the above gaussian
histograms I observe an exess for prob close to 1.

  Cheers,
  Andy.



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