{ using namespace RooFit ; using namespace RooStats ;
    RooWorkspace w("CMGWs","CMGWs");
    w.factory("Poisson::countingModel(obs[150,0,300], sum(s[50,0,120]*ratioSigEff[1.,0,2.],b[100]*ratioBkgEff[1.,0.,2.]))");
    w.factory("Gaussian::sigConstraint(1,ratioSigEff,0.05)"); // 5% signal efficiency uncertainty
    w.factory("Gaussian::bkgConstraint(1,ratioBkgEff,0.1)"); // 10% background efficiency uncertainty
    w.factory("PROD::modelWithConstraints(countingModel,sigConstraint,bkgConstraint)");

    RooAbsPdf* modelWithConstraints = w.pdf("modelWithConstraints"); // get the model
    RooRealVar* obs = w.var("obs"); RooRealVar* s = w.var("s");

    // Create an example dataset with 160 observed events
    obs->setVal(160.);
    RooDataSet* data = new RooDataSet("exData","exData", RooArgSet(*obs));
    data->add(*obs);
    
    // Model Config
    ModelConfig modelConfig(&w);
    modelConfig.SetPdf(*modelWithConstraints);
    modelConfig.SetParametersOfInterest(RooArgSet(*s));

    // Configure the FC calculator
    FeldmanCousins fc(*data, modelConfig);
    fc.UseAdaptiveSampling(true); // Optimise the toys generation
    fc.FluctuateNumDataEntries(false); // Counting dataset has 1 entry
    fc.SetNBins(40); // number of points to test per parameter
    fc.SetTestSize(.05);
    
    // Start it!
    ConfInterval* fcint = fc.GetInterval();

    // Get Lower and Upper limits from FeldmanCousins with profile construction
    double ul = ((PointSetInterval*) fcint)->UpperLimit(*s);
    double ll = ((PointSetInterval*) fcint)->LowerLimit(*s);
    cout << "FC interval: [ " << ll << " - " << ul << " ]\n"; }