{
  using namespace RooStats;
  
  double credLevel= .68; double size = 1.-credLevel;
  RooWorkspace *w = new RooWorkspace("CMGWs","CMG workspace");
  w.factory("Gaussian::signal(imass[110,120],sigmean[115],sigwidth[1])");
  w.factory("Exponential::background(imass,exppar[-.1])");
  w.factory("SUM::model(nsig[50,0.1,120]*signal,nbkg[1000,0,10000]*background)");  

  w.factory("Uniform::priorPOI(nsig)"); //prior1
  w.factory("GenericPdf::priorPOI2('1/sqrt(@0)',nsig)"); //prior2

  // Get the interesting objects
  RooAbsPdf* model = w.pdf("model");
  RooRealVar* nsig = w.var("nsig");
  
  // Create an example dataset (binned is fast..)
  RooDataHist* data = model->generateBinned(*w.var("imass"));

  // Model Config 1
  ModelConfig modelConfig(new RooWorkspace());
  modelConfig.SetPdf(*model);
  modelConfig.SetParametersOfInterest(RooArgSet(*nsig));
  modelConfig.SetPriorPdf(*w.pdf("priorPOI"));
    
  // example use of MCMCInterval
  MCMCCalculator mccalc(*data, modelConfig);
  mccalc.SetTestSize(size);
  // special options
  mccalc.SetNumBins(40);	  // bins used internally for representing posterior
  mccalc.SetNumBurnInSteps(500); // first N steps to be ignored as burn-in
  mccalc.SetNumIters(500000);    // how long to run chain
  mccalc.SetLeftSideTailFraction(0.5); // for central interval
  MCMCInterval* interval = mccalc.GetInterval();
  double cl = mccalc.ConfidenceLevel();
    cout << "* " << cl <<" CL central interval: [ " << interval->LowerLimit(*nsig) 
         << " - " << interval->UpperLimit(*nsig) << " ]" << endl;
  MCMCIntervalPlot plot(*interval);plot.SetLineColor(kBlue);plot->SetLineWidth(2);
  
  modelConfig.SetPriorPdf(*w.pdf("priorPOI2"));
  MCMCCalculator mccalcsqrt(*data, modelConfig);
  mccalcsqrt.SetTestSize(size);
  // special options
  mccalcsqrt.SetNumBins(40);	  // bins used internally for representing posterior
  mccalcsqrt.SetNumBurnInSteps(500); // first N steps to be ignored as burn-in
  mccalcsqrt.SetNumIters(500000);    // how long to run chain
  mccalcsqrt.SetLeftSideTailFraction(0.5); // for central interval
  interval = mccalcsqrt.GetInterval();
  double cl = mccalcsqrt.ConfidenceLevel();
    cout << "* " << cl <<" CL central interval: [ " << interval->LowerLimit(*nsig) 
         << " - " << interval->UpperLimit(*nsig) << " ]" << endl;
  MCMCIntervalPlot plotsqrt(*interval);plotsqrt.SetLineColor(kBlue);plotsqrt->SetLineWidth(2);
  
  TCanvas c1("MCMCCR","MCMC Calculator Result",800,400);
  c1.Divide(2,1); 
  c1.cd(1);plot->Draw();
  c1.cd(2);plotsqrt->Draw();    
  
}