diff --git a/test/stressRooFit.cxx b/test/stressRooFit.cxx
index 45a23456d1ee6528c1427803a2101ff556d99d91..b184049f4afd059b3720a46099692bd88d022dc7 100644
--- a/test/stressRooFit.cxx
+++ b/test/stressRooFit.cxx
@@ -357,7 +357,7 @@ Int_t stressRooFit()
    Bool_t doDump      = kFALSE ;
    Bool_t doTreeStore = kFALSE ;
 
-   string refFileName = "http://root.cern.ch/files/stressRooFit_v534_ref.root" ;
+   string refFileName = "http://root.cern.ch/files/stressRooFit_v608_ref.root" ;
    return stressRooFit(refFileName.c_str(),doWrite,doVerbose,oneTest,dryRun,doDump,doTreeStore);
 }
 
diff --git a/test/stressRooFit_tests.cxx b/test/stressRooFit_tests.cxx
index c79f88445977bf550d42a2d34ba3a528ce1cf737..70f646413b0169ea57c193b939b94d2913184c3f 100644
--- a/test/stressRooFit_tests.cxx
+++ b/test/stressRooFit_tests.cxx
@@ -938,7 +938,7 @@ public:
 
     // Build Chebychev polynomial p.d.f.
     RooRealVar a0("a0","a0",0.5,0.,1.) ;
-    RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+    RooRealVar a1("a1","a1",-0.2,-1.,1.) ; 
     RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
 
@@ -1065,7 +1065,7 @@ public:
 
     // Build Chebychev polynomial p.d.f.
     RooRealVar a0("a0","a0",0.5,0.,1.) ;
-    RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+    RooRealVar a1("a1","a1",-0.2,-1.,1.) ; 
     RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
     // Sum the signal components into a composite signal p.d.f.
@@ -1273,7 +1273,7 @@ public:
 
     // Build Chebychev polynomial p.d.f.
     RooRealVar a0("a0","a0",0.5,0.,1.) ;
-    RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+    RooRealVar a1("a1","a1",-0.2,-1.,1.) ;
     RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
     // Sum the signal components into a composite signal p.d.f.
@@ -1369,7 +1369,7 @@ public:
 
     // Build Chebychev polynomial p.d.f.
     RooRealVar a0("a0","a0",0.5,0.,1.) ;
-    RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+    RooRealVar a1("a1","a1",-0.2,-1.,1.) ;
     RooChebychev bkg1("bkg1","Background 1",x,RooArgSet(a0,a1)) ;
 
     // Build expontential pdf
@@ -4417,7 +4417,7 @@ public:
 
   // Build Chebychev polynomial p.d.f.
   RooRealVar a0("a0","a0",0.5,0.,1.) ;
-  RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+  RooRealVar a1("a1","a1",-0.2,-1.,1.) ;
   RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
   // Sum the signal components into a composite signal p.d.f.
@@ -4810,7 +4810,7 @@ public:
 
   // Build Chebychev polynomial p.d.f.
   RooRealVar a0("a0","a0",0.5,0.,1.) ;
-  RooRealVar a1("a1","a1",-0.2) ;
+  RooRealVar a1("a1","a1",-0.2,-1.,1.) ;
   RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
   // Sum the signal components into a composite signal p.d.f.
@@ -6028,7 +6028,7 @@ public:
 
   // Build Chebychev polynomial p.d.f.
   RooRealVar a0("a0","a0",0.5,0.,1.) ;
-  RooRealVar a1("a1","a1",-0.2,-1,1.) ;
+  RooRealVar a1("a1","a1",-0.2,-1.,1.) ;
   RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
   // Sum the signal components into a composite signal p.d.f.
diff --git a/tutorials/roofit/rf201_composite.C b/tutorials/roofit/rf201_composite.C
index ef3b6194d44a64eab257b44fca566ce60e05958f..c2709e023d7d1b8548bcd64de590cb23e4602aa4 100644
--- a/tutorials/roofit/rf201_composite.C
+++ b/tutorials/roofit/rf201_composite.C
@@ -41,7 +41,7 @@ void rf201_composite()
 
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
 
diff --git a/tutorials/roofit/rf202_extendedmlfit.C b/tutorials/roofit/rf202_extendedmlfit.C
index 88932406de98d56d93b2311c42b3db6447c99fa1..9f37e38f7b9e1d5e306fda396e0a5c6d5db37850 100644
--- a/tutorials/roofit/rf202_extendedmlfit.C
+++ b/tutorials/roofit/rf202_extendedmlfit.C
@@ -41,7 +41,7 @@ void rf202_extendedmlfit()
 
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
    // Sum the signal components into a composite signal p.d.f.
diff --git a/tutorials/roofit/rf204_extrangefit.C b/tutorials/roofit/rf204_extrangefit.C
index be277c796d2c7b07a1e4a5141b9926697af8232c..616e092ba2ac6d148d2a6785e18e6d9c6d0d34e8 100644
--- a/tutorials/roofit/rf204_extrangefit.C
+++ b/tutorials/roofit/rf204_extrangefit.C
@@ -44,7 +44,7 @@ void rf204_extrangefit()
 
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
    // Sum the signal components into a composite signal p.d.f.
diff --git a/tutorials/roofit/rf205_compplot.C b/tutorials/roofit/rf205_compplot.C
index 8506001219917261bf300d9542fb957bbfc2f861..6f0499b60ace2c6153fa2c39945710ed24df2eef 100644
--- a/tutorials/roofit/rf205_compplot.C
+++ b/tutorials/roofit/rf205_compplot.C
@@ -44,7 +44,7 @@ void rf205_compplot()
 
    // Build Chebychev polynomial p.d.f.
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg1("bkg1","Background 1",x,RooArgSet(a0,a1)) ;
 
    // Build exponential pdf
diff --git a/tutorials/roofit/rf206_treevistools.C b/tutorials/roofit/rf206_treevistools.C
index 7e211be80a4e3a0f29c023a8ae78ce6aa4d57c95..f7ec2941ab56806638fb28f5dfff001ae796629e 100644
--- a/tutorials/roofit/rf206_treevistools.C
+++ b/tutorials/roofit/rf206_treevistools.C
@@ -43,7 +43,7 @@ void rf206_treevistools()
 
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg1("bkg1","Background 1",x,RooArgSet(a0,a1)) ;
 
    // Build expontential pdf
diff --git a/tutorials/roofit/rf207_comptools.C b/tutorials/roofit/rf207_comptools.C
index b1986b755837a6ad6c874131b0853ce478bcbfb5..cbd3eac052e40b283d0d036ba391d0f366220f2a 100644
--- a/tutorials/roofit/rf207_comptools.C
+++ b/tutorials/roofit/rf207_comptools.C
@@ -41,7 +41,7 @@ void rf207_comptools()
 
    // Build Chebychev polynomial p.d.f.
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg1("bkg1","Background 1",x,RooArgSet(a0,a1)) ;
 
    // Build exponential pdf
diff --git a/tutorials/roofit/rf407_latextables.C b/tutorials/roofit/rf407_latextables.C
index 72457d4893896a9441a155461e78fa4261068781..d9f5084dd8d7d1ee66144603a05f4207e56a480a 100644
--- a/tutorials/roofit/rf407_latextables.C
+++ b/tutorials/roofit/rf407_latextables.C
@@ -43,7 +43,7 @@ void rf407_latextables()
 
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg1("bkg1","Background 1",x,RooArgSet(a0,a1)) ;
 
    // Build expontential pdf
diff --git a/tutorials/roofit/rf502_wspacewrite.C b/tutorials/roofit/rf502_wspacewrite.C
index 4d8f1f3cc53d4e2549632b7624c0a98ca292675b..5e74784d8490e240c5c7ca75c4f4256e2e1c1f52 100644
--- a/tutorials/roofit/rf502_wspacewrite.C
+++ b/tutorials/roofit/rf502_wspacewrite.C
@@ -44,7 +44,7 @@ void rf502_wspacewrite()
 
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
    // Sum the signal components into a composite signal p.d.f.
diff --git a/tutorials/roofit/rf509_wsinteractive.C b/tutorials/roofit/rf509_wsinteractive.C
index 3aa718d3152d9a3118ce45710e64b269697a102c..17f966b41c322db1dc3d415bef7ee8856d6bc909 100644
--- a/tutorials/roofit/rf509_wsinteractive.C
+++ b/tutorials/roofit/rf509_wsinteractive.C
@@ -119,7 +119,7 @@ void fillWorkspace(RooWorkspace& w)
 
    // Build Chebychev polynomial p.d.f.
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
    // Sum the signal components into a composite signal p.d.f.
diff --git a/tutorials/roofit/rf510_wsnamedsets.C b/tutorials/roofit/rf510_wsnamedsets.C
index affb5931d81f2d1a3e359406f660fd4183ac9fe2..dc3d994b9ea97780cd1128cd0a69de2a17f5f557 100644
--- a/tutorials/roofit/rf510_wsnamedsets.C
+++ b/tutorials/roofit/rf510_wsnamedsets.C
@@ -94,7 +94,7 @@ void fillWorkspace(RooWorkspace& w)
 
    // Build Chebychev polynomial p.d.f.
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
    // Sum the signal components into a composite signal p.d.f.
diff --git a/tutorials/roofit/rf511_wsfactory_basic.C b/tutorials/roofit/rf511_wsfactory_basic.C
index f0d51cb3884e176612accd61aac757fca710d863..6537ce38456f16726d6239521229e2ae4c08668b 100644
--- a/tutorials/roofit/rf511_wsfactory_basic.C
+++ b/tutorials/roofit/rf511_wsfactory_basic.C
@@ -45,7 +45,7 @@ void rf511_wsfactory_basic(Bool_t compact=kFALSE)
       // Use object factory to build p.d.f. of tutorial rs502_wspacewrite
       w->factory("Gaussian::sig1(x[-10,10],mean[5,0,10],0.5)") ;
       w->factory("Gaussian::sig2(x,mean,1)") ;
-      w->factory("Chebychev::bkg(x,{a0[0.5,0.,1],a1[-0.2,0.,1.]})") ;
+      w->factory("Chebychev::bkg(x,{a0[0.5,0.,1],a1[0.2,0.,1.]})") ;
       w->factory("SUM::sig(sig1frac[0.8,0.,1.]*sig1,sig2)") ;
       w->factory("SUM::model(bkgfrac[0.5,0.,1.]*bkg,sig)") ;
 
@@ -55,7 +55,7 @@ void rf511_wsfactory_basic(Bool_t compact=kFALSE)
       //  - Contracted to a single line recursive expression,
       //  - Omitting explicit names for components that are not referred to explicitly later
 
-      w->factory("SUM::model(bkgfrac[0.5,0.,1.]*Chebychev::bkg(x[-10,10],{a0[0.5,0.,1],a1[-0.2,0.,1.]}),"
+      w->factory("SUM::model(bkgfrac[0.5,0.,1.]*Chebychev::bkg(x[-10,10],{a0[0.5,0.,1],a1[0.2,0.,1.]}),"
                                                 "SUM(sig1frac[0.8,0.,1.]*Gaussian(x,mean[5,0,10],0.5), Gaussian(x,mean,1)))") ;
    }
 
diff --git a/tutorials/roofit/rf602_chi2fit.C b/tutorials/roofit/rf602_chi2fit.C
index 0bd45faa8bcf0958e57d3aa9dfce5d5f909c57af..4f988219de1f1d6daf4bdeaaa755349fa18846cd 100644
--- a/tutorials/roofit/rf602_chi2fit.C
+++ b/tutorials/roofit/rf602_chi2fit.C
@@ -43,7 +43,7 @@ void rf602_chi2fit()
    
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.) ;
-   RooRealVar a1("a1","a1",-0.2,0.,1.) ;
+   RooRealVar a1("a1","a1",0.2,0.,1.) ;
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1)) ;
 
    // Sum the signal components into a composite signal p.d.f.