diff --git a/applications/lazstats/source/forms/simulations/fprobunit.lfm b/applications/lazstats/source/forms/simulations/fprobunit.lfm
index f5b132269..9afce89c5 100644
--- a/applications/lazstats/source/forms/simulations/fprobunit.lfm
+++ b/applications/lazstats/source/forms/simulations/fprobunit.lfm
@@ -29,7 +29,7 @@ object FForm: TFForm
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -45,7 +45,7 @@ object FForm: TFForm
     BorderSpacing.Right = 12
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -61,7 +61,7 @@ object FForm: TFForm
     BorderSpacing.Right = 12
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -79,7 +79,7 @@ object FForm: TFForm
     BorderSpacing.Bottom = 8
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -108,18 +108,18 @@ object FForm: TFForm
     BevelOuter = bvNone
     ClientHeight = 85
     ClientWidth = 412
-    TabOrder = 4
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideTop.Control = FEdit
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = Label4
       AnchorSideRight.Side = asrBottom
-      Left = 88
+      Left = 102
       Height = 15
       Top = 4
-      Width = 117
+      Width = 103
       Anchors = [akTop, akRight]
-      Caption = 'Given: An F statistic = '
+      Caption = 'Given: An F statistic'
       ParentColor = False
     end
     object FEdit: TEdit
@@ -141,12 +141,12 @@ object FForm: TFForm
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = Label4
       AnchorSideRight.Side = asrBottom
-      Left = 88
+      Left = 91
       Height = 15
       Top = 31
-      Width = 117
+      Width = 114
       Anchors = [akTop, akRight]
-      Caption = 'with Deg. Freedom of '
+      Caption = 'with deg. freedom of '
       ParentColor = False
     end
     object DF1Edit: TEdit
@@ -199,7 +199,7 @@ object FForm: TFForm
       Height = 15
       Top = 66
       Width = 205
-      Caption = 'then the probability of a larger value = '
+      Caption = 'then the probability of a larger value  is'
       ParentColor = False
     end
     object ProbEdit: TEdit
diff --git a/applications/lazstats/source/forms/simulations/fprobunit.pas b/applications/lazstats/source/forms/simulations/fprobunit.pas
index edf8e6fc6..e6e734e8c 100644
--- a/applications/lazstats/source/forms/simulations/fprobunit.pas
+++ b/applications/lazstats/source/forms/simulations/fprobunit.pas
@@ -41,8 +41,10 @@ var
 
 implementation
 
+{$R *.lfm}
+
 uses
-  Math, MathUnit;
+  Math, MathUnit, Utils;
 
 { TFForm }
 
@@ -55,14 +57,33 @@ begin
 end;
 
 procedure TFForm.ComputeBtnClick(Sender: TObject);
-VAR
-  F, df1, df2, prob : extended;
+var
+  F, prob: Double;
+  df1, df2: Integer;
 begin
-   F := StrToFloat(FEdit.Text);
-   df1 := StrToFloat(DF1Edit.Text);
-   df2 := StrToFloat(DF2Edit.Text);
-   prob := ProbF(F,df1,df2);
-   ProbEdit.Text := Format('%6.4f',[prob]);
+  if not MyTryStrToFloat(FEdit.Text, F) then
+  begin
+    FEdit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+
+  if not TryStrToInt(DF1Edit.Text, df1) then
+  begin
+    DF1Edit.SetFocus;
+    ErrorMsg('No valid integer (must be positive).');
+    exit;
+  end;
+
+  if not TryStrToInt(DF2Edit.Text, df2) then
+  begin
+    DF2Edit.SetFocus;
+    ErrorMsg('No valid integer (must be positive).');
+    exit;
+  end;
+
+  prob := ProbF(F, df1, df2);
+  ProbEdit.Text := Format('%6.4f', [prob]);
 end;
 
 procedure TFForm.FormActivate(Sender: TObject);
@@ -77,8 +98,5 @@ begin
 end;
 
 
-initialization
-  {$I fprobunit.lrs}
-
 end.
 
diff --git a/applications/lazstats/source/forms/simulations/inversezunit.lfm b/applications/lazstats/source/forms/simulations/inversezunit.lfm
index 94829005a..4ff95baea 100644
--- a/applications/lazstats/source/forms/simulations/inversezunit.lfm
+++ b/applications/lazstats/source/forms/simulations/inversezunit.lfm
@@ -29,7 +29,7 @@ object InversezForm: TInversezForm
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -45,7 +45,7 @@ object InversezForm: TInversezForm
     BorderSpacing.Right = 12
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -61,7 +61,7 @@ object InversezForm: TInversezForm
     BorderSpacing.Right = 12
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -78,7 +78,7 @@ object InversezForm: TInversezForm
     BorderSpacing.Right = 16
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -97,29 +97,29 @@ object InversezForm: TInversezForm
     AnchorSideLeft.Control = Owner
     AnchorSideLeft.Side = asrCenter
     AnchorSideTop.Control = Owner
-    Left = 54
+    Left = 65
     Height = 54
     Top = 8
-    Width = 239
+    Width = 217
     AutoSize = True
     BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BevelOuter = bvNone
     ClientHeight = 54
-    ClientWidth = 239
-    TabOrder = 4
+    ClientWidth = 217
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideTop.Control = ProbEdit
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = Label2
       AnchorSideRight.Side = asrBottom
-      Left = 8
+      Left = 0
       Height = 15
       Top = 4
-      Width = 135
+      Width = 121
       Anchors = [akTop, akRight]
-      Caption = 'Cumulative Probability = '
+      Caption = 'Cumulative Probability'
       ParentColor = False
     end
     object ProbEdit: TEdit
@@ -127,7 +127,7 @@ object InversezForm: TInversezForm
       AnchorSideTop.Control = Panel1
       AnchorSideRight.Control = ZEdit
       AnchorSideRight.Side = asrBottom
-      Left = 151
+      Left = 129
       Height = 23
       Top = 0
       Width = 88
@@ -143,8 +143,8 @@ object InversezForm: TInversezForm
       Left = 0
       Height = 15
       Top = 35
-      Width = 143
-      Caption = 'Corresponds to a z value = '
+      Width = 121
+      Caption = 'Corresponding z value '
       ParentColor = False
     end
     object ZEdit: TEdit
@@ -152,7 +152,7 @@ object InversezForm: TInversezForm
       AnchorSideLeft.Side = asrBottom
       AnchorSideTop.Control = ProbEdit
       AnchorSideTop.Side = asrBottom
-      Left = 151
+      Left = 129
       Height = 23
       Top = 31
       Width = 88
diff --git a/applications/lazstats/source/forms/simulations/inversezunit.pas b/applications/lazstats/source/forms/simulations/inversezunit.pas
index 78fbc11b9..df2ec3848 100644
--- a/applications/lazstats/source/forms/simulations/inversezunit.pas
+++ b/applications/lazstats/source/forms/simulations/inversezunit.pas
@@ -6,8 +6,7 @@ interface
 
 uses
   Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
-  StdCtrls, ExtCtrls,
-  Functionslib;
+  StdCtrls, ExtCtrls;
 
 type
 
@@ -38,8 +37,10 @@ var
 
 implementation
 
+{$R *.lfm}
+
 uses
-  Math;
+  Math, MathUnit, Utils;
 
 { TInversezForm }
 
@@ -50,14 +51,17 @@ begin
 end;
 
 procedure TInversezForm.ComputeBtnClick(Sender: TObject);
-VAR
-  Prob, Zscore : double;
-  outvalue : string;
+var
+  prob, zScore: double;
 begin
-  Prob := StrToFloat(ProbEdit.Text);
-  Zscore := inversez(Prob);
-  outvalue := format('%6.4f',[Zscore]);
-  ZEdit.Text := outvalue;
+  if not MyTryStrToFloat(ProbEdit.Text, prob) then
+  begin
+    ProbEdit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+  zScore := InverseNormalDist(prob);
+  ZEdit.Text := Format('%6.4f', [zScore]);
 end;
 
 procedure TInversezForm.FormActivate(Sender: TObject);
@@ -71,8 +75,5 @@ begin
   ReturnBtn.Constraints.MinWidth := w;
 end;
 
-initialization
-  {$I inversezunit.lrs}
-
 end.
 
diff --git a/applications/lazstats/source/forms/simulations/probchisqrunit.lfm b/applications/lazstats/source/forms/simulations/probchisqrunit.lfm
index 2337d733a..c458e62e7 100644
--- a/applications/lazstats/source/forms/simulations/probchisqrunit.lfm
+++ b/applications/lazstats/source/forms/simulations/probchisqrunit.lfm
@@ -26,7 +26,7 @@ object ChiSqrProbForm: TChiSqrProbForm
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = ReturnBtn
@@ -40,7 +40,7 @@ object ChiSqrProbForm: TChiSqrProbForm
     BorderSpacing.Right = 8
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = ReturnBtn
@@ -54,7 +54,7 @@ object ChiSqrProbForm: TChiSqrProbForm
     BorderSpacing.Right = 8
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -73,7 +73,7 @@ object ChiSqrProbForm: TChiSqrProbForm
     BorderSpacing.Bottom = 8
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -92,18 +92,18 @@ object ChiSqrProbForm: TChiSqrProbForm
     AnchorSideLeft.Control = Owner
     AnchorSideLeft.Side = asrCenter
     AnchorSideTop.Control = Owner
-    Left = 86
+    Left = 93
     Height = 85
     Top = 8
-    Width = 217
+    Width = 203
     AutoSize = True
     BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BevelOuter = bvNone
     ClientHeight = 85
-    ClientWidth = 217
-    TabOrder = 4
+    ClientWidth = 203
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideTop.Control = ChiSqrEdit
       AnchorSideTop.Side = asrCenter
@@ -112,10 +112,10 @@ object ChiSqrProbForm: TChiSqrProbForm
       Left = 30
       Height = 15
       Top = 4
-      Width = 105
+      Width = 91
       Anchors = [akTop, akRight]
       BorderSpacing.Left = 8
-      Caption = 'Chisquared value = '
+      Caption = 'Chisquared value'
       ParentColor = False
     end
     object ChiSqrEdit: TEdit
@@ -123,7 +123,7 @@ object ChiSqrProbForm: TChiSqrProbForm
       AnchorSideTop.Control = Panel1
       AnchorSideRight.Control = ProbEdit
       AnchorSideRight.Side = asrBottom
-      Left = 143
+      Left = 129
       Height = 23
       Top = 0
       Width = 74
@@ -140,10 +140,10 @@ object ChiSqrProbForm: TChiSqrProbForm
       Left = 24
       Height = 15
       Top = 31
-      Width = 111
+      Width = 97
       Anchors = [akTop, akRight]
       BorderSpacing.Left = 8
-      Caption = 'with deg. freedom = '
+      Caption = 'with deg. freedom'
       ParentColor = False
     end
     object DFEdit: TEdit
@@ -152,7 +152,7 @@ object ChiSqrProbForm: TChiSqrProbForm
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = ProbEdit
       AnchorSideRight.Side = asrBottom
-      Left = 143
+      Left = 129
       Height = 23
       Top = 27
       Width = 74
@@ -169,8 +169,8 @@ object ChiSqrProbForm: TChiSqrProbForm
       Left = 0
       Height = 15
       Top = 66
-      Width = 135
-      Caption = 'Probability larger value = '
+      Width = 121
+      Caption = 'Probability larger value'
       ParentColor = False
     end
     object ProbEdit: TEdit
@@ -178,7 +178,7 @@ object ChiSqrProbForm: TChiSqrProbForm
       AnchorSideLeft.Side = asrBottom
       AnchorSideTop.Control = DFEdit
       AnchorSideTop.Side = asrBottom
-      Left = 143
+      Left = 129
       Height = 23
       Top = 62
       Width = 74
diff --git a/applications/lazstats/source/forms/simulations/probchisqrunit.pas b/applications/lazstats/source/forms/simulations/probchisqrunit.pas
index 579bde031..83ff41c53 100644
--- a/applications/lazstats/source/forms/simulations/probchisqrunit.pas
+++ b/applications/lazstats/source/forms/simulations/probchisqrunit.pas
@@ -40,8 +40,10 @@ var
 
 implementation
 
+{$R *.lfm}
+
 uses
-  Math;
+  Math, MathUnit, Utils;
 
 { TChiSqrProbForm }
 
@@ -53,16 +55,25 @@ begin
 end;
 
 procedure TChiSqrProbForm.ComputeBtnClick(Sender: TObject);
-VAR
-  ChiSqr, Prob : double;
-  DF : integer;
-  outvalue : string;
+var
+  chiSqr, prob: double;
+  DF: integer;
 begin
-  ChiSqr := StrToFloat(ChiSqrEdit.Text);
-  DF := StrToInt(DFEdit.Text);
-  Prob := 1.0 - chisquaredprob(ChiSqr,DF);
-  outvalue := format('%6.4f',[Prob]);
-  ProbEdit.Text := outvalue;
+  if not MyTryStrToFloat(ChiSqrEdit.Text, chiSqr) then
+  begin
+    ChiSqrEdit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+
+  if not TryStrToInt(DFEdit.Text, DF) or (DF <= 0) then begin
+    DFEdit.SetFocus;
+    ErrorMsg('No a valid integer (must be positive).');
+    exit;
+  end;
+
+  prob := 1.0 - ChiSquaredProb(ChiSqr, DF);
+  ProbEdit.Text := Format('%6.4f', [prob]);
 end;
 
 procedure TChiSqrProbForm.FormActivate(Sender: TObject);
@@ -76,8 +87,5 @@ begin
   ReturnBtn.Constraints.MinWidth := w;
 end;
 
-initialization
-  {$I probchisqrunit.lrs}
-
 end.
 
diff --git a/applications/lazstats/source/forms/simulations/probsmallerzunit.lfm b/applications/lazstats/source/forms/simulations/probsmallerzunit.lfm
index 17c13f1a8..95016dbf4 100644
--- a/applications/lazstats/source/forms/simulations/probsmallerzunit.lfm
+++ b/applications/lazstats/source/forms/simulations/probsmallerzunit.lfm
@@ -29,7 +29,7 @@ object ProbSmallerzForm: TProbSmallerzForm
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -45,7 +45,7 @@ object ProbSmallerzForm: TProbSmallerzForm
     BorderSpacing.Right = 12
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -61,7 +61,7 @@ object ProbSmallerzForm: TProbSmallerzForm
     BorderSpacing.Right = 12
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -79,38 +79,38 @@ object ProbSmallerzForm: TProbSmallerzForm
     BorderSpacing.Bottom = 8
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Panel1: TPanel
     AnchorSideLeft.Control = Owner
     AnchorSideLeft.Side = asrCenter
-    Left = 57
+    Left = 64
     Height = 54
     Top = 4
-    Width = 194
+    Width = 180
     AutoSize = True
     BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BevelOuter = bvNone
     ClientHeight = 54
-    ClientWidth = 194
-    TabOrder = 4
+    ClientWidth = 180
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideTop.Control = zEdit
       AnchorSideTop.Side = asrCenter
       Left = 0
       Height = 15
       Top = 4
-      Width = 103
-      Caption = 'Observed z score = '
+      Width = 89
+      Caption = 'Observed z score'
       ParentColor = False
     end
     object zEdit: TEdit
       AnchorSideLeft.Control = Label1
       AnchorSideLeft.Side = asrBottom
       AnchorSideTop.Control = Panel1
-      Left = 111
+      Left = 97
       Height = 23
       Top = 0
       Width = 83
@@ -127,9 +127,9 @@ object ProbSmallerzForm: TProbSmallerzForm
       Left = 13
       Height = 15
       Top = 35
-      Width = 90
+      Width = 76
       Anchors = [akTop, akRight]
-      Caption = 'Probability < z = '
+      Caption = 'Probability < z'
       ParentColor = False
     end
     object ProbzEdit: TEdit
@@ -138,7 +138,7 @@ object ProbSmallerzForm: TProbSmallerzForm
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = zEdit
       AnchorSideRight.Side = asrBottom
-      Left = 111
+      Left = 97
       Height = 23
       Top = 31
       Width = 83
diff --git a/applications/lazstats/source/forms/simulations/probsmallerzunit.pas b/applications/lazstats/source/forms/simulations/probsmallerzunit.pas
index f9563cc5d..6c16267fd 100644
--- a/applications/lazstats/source/forms/simulations/probsmallerzunit.pas
+++ b/applications/lazstats/source/forms/simulations/probsmallerzunit.pas
@@ -6,8 +6,7 @@ interface
 
 uses
   Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
-  StdCtrls, ExtCtrls,
-  Functionslib;
+  StdCtrls, ExtCtrls;
 
 type
 
@@ -38,26 +37,31 @@ var
 
 implementation
 
+{$R *.lfm}
+
 uses
-  Math;
+  Math, MathUnit, Utils;
 
 { TProbSmallerzForm }
 
 procedure TProbSmallerzForm.ResetBtnClick(Sender: TObject);
 begin
-    zEdit.Text := '';
-    ProbzEdit.Text := '';
+  zEdit.Text := '';
+  ProbzEdit.Text := '';
 end;
 
 procedure TProbSmallerzForm.ComputeBtnClick(Sender: TObject);
-VAR
-   zprob, z : double;
-   outvalue : string;
+var
+  zprob, z: double;
 begin
-    z := StrToFloat(zEdit.Text);
-    zprob := probz(z);
-    outvalue := format('%6.4f',[zprob]);
-    ProbzEdit.Text := outvalue;
+  if not MyTryStrToFloat(zEdit.Text, z) then
+  begin
+    zEdit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+  zProb := NormalDist(z);
+  ProbzEdit.Text := Format('%6.4f', [zProb]);
 end;
 
 procedure TProbSmallerzForm.FormActivate(Sender: TObject);
@@ -71,8 +75,5 @@ begin
   ReturnBtn.Constraints.MinWidth := w;
 end;
 
-initialization
-  {$I probsmallerzunit.lrs}
-
 end.
 
diff --git a/applications/lazstats/source/forms/simulations/probzunit.lfm b/applications/lazstats/source/forms/simulations/probzunit.lfm
index 07dd9e9ac..4d053baa0 100644
--- a/applications/lazstats/source/forms/simulations/probzunit.lfm
+++ b/applications/lazstats/source/forms/simulations/probzunit.lfm
@@ -29,7 +29,7 @@ object ProbzForm: TProbzForm
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -45,7 +45,7 @@ object ProbzForm: TProbzForm
     BorderSpacing.Right = 12
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -61,7 +61,7 @@ object ProbzForm: TProbzForm
     BorderSpacing.Right = 12
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -79,7 +79,7 @@ object ProbzForm: TProbzForm
     BorderSpacing.Bottom = 8
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -98,18 +98,18 @@ object ProbzForm: TProbzForm
     AnchorSideLeft.Control = Owner
     AnchorSideLeft.Side = asrCenter
     AnchorSideTop.Control = Owner
-    Left = 58
+    Left = 65
     Height = 55
     Top = 8
-    Width = 194
+    Width = 180
     AutoSize = True
     BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BevelOuter = bvNone
     ClientHeight = 55
-    ClientWidth = 194
-    TabOrder = 4
+    ClientWidth = 180
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideLeft.Control = Panel1
       AnchorSideTop.Control = zEdit
@@ -117,14 +117,14 @@ object ProbzForm: TProbzForm
       Left = 0
       Height = 15
       Top = 4
-      Width = 103
-      Caption = 'Observed z score = '
+      Width = 89
+      Caption = 'Observed z score'
       ParentColor = False
     end
     object zEdit: TEdit
       AnchorSideLeft.Control = Label1
       AnchorSideLeft.Side = asrBottom
-      Left = 111
+      Left = 97
       Height = 23
       Top = 0
       Width = 83
@@ -141,16 +141,16 @@ object ProbzForm: TProbzForm
       Left = 13
       Height = 15
       Top = 36
-      Width = 90
+      Width = 76
       Anchors = [akTop, akRight]
-      Caption = 'Probability > z = '
+      Caption = 'Probability > z'
       ParentColor = False
     end
     object ProbzEdit: TEdit
       AnchorSideLeft.Control = zEdit
       AnchorSideRight.Control = zEdit
       AnchorSideRight.Side = asrBottom
-      Left = 111
+      Left = 97
       Height = 23
       Top = 32
       Width = 83
diff --git a/applications/lazstats/source/forms/simulations/probzunit.pas b/applications/lazstats/source/forms/simulations/probzunit.pas
index c30c2c0d8..a56130a73 100644
--- a/applications/lazstats/source/forms/simulations/probzunit.pas
+++ b/applications/lazstats/source/forms/simulations/probzunit.pas
@@ -6,8 +6,7 @@ interface
 
 uses
   Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
-  StdCtrls, ExtCtrls,
-  FunctionsLib;
+  StdCtrls, ExtCtrls;
 
 type
 
@@ -38,8 +37,10 @@ var
 
 implementation
 
+{$R *.lfm}
+
 uses
-  Math;
+  Math, MathUnit, Utils;
 
 { TProbzForm }
 
@@ -50,14 +51,17 @@ begin
 end;
 
 procedure TProbzForm.ComputeBtnClick(Sender: TObject);
-VAR
-   zprob, z : double;
-   outvalue : string;
+var
+  zprob, z: double;
 begin
-   z := StrToFloat(zEdit.Text);
-   zprob := 1.0 - probz(z);
-   outvalue := format('%6.4f',[zprob]);
-   ProbzEdit.Text := outvalue;
+  if not MyTryStrToFloat(zEdit.Text, z) then
+  begin
+    zEdit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+  zProb := 1.0 - NormalDist(z);
+  ProbzEdit.Text := Format('%6.4f', [zProb]);
 end;
 
 procedure TProbzForm.FormActivate(Sender: TObject);
@@ -71,8 +75,5 @@ begin
   ReturnBtn.Constraints.MinWidth := w;
 end;
 
-initialization
-  {$I probzunit.lrs}
-
 end.
 
diff --git a/applications/lazstats/source/forms/simulations/tprobunit.lfm b/applications/lazstats/source/forms/simulations/tprobunit.lfm
index f30404f21..ad0480321 100644
--- a/applications/lazstats/source/forms/simulations/tprobunit.lfm
+++ b/applications/lazstats/source/forms/simulations/tprobunit.lfm
@@ -29,7 +29,7 @@ object TProbForm: TTProbForm
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -45,7 +45,7 @@ object TProbForm: TTProbForm
     BorderSpacing.Right = 12
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -61,7 +61,7 @@ object TProbForm: TTProbForm
     BorderSpacing.Right = 12
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
@@ -79,7 +79,7 @@ object TProbForm: TTProbForm
     BorderSpacing.Bottom = 8
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -98,18 +98,18 @@ object TProbForm: TTProbForm
     AnchorSideLeft.Control = Owner
     AnchorSideLeft.Side = asrCenter
     AnchorSideTop.Control = Owner
-    Left = 87
+    Left = 94
     Height = 85
     Top = 8
-    Width = 217
+    Width = 203
     AutoSize = True
     BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BevelOuter = bvNone
     ClientHeight = 85
-    ClientWidth = 217
-    TabOrder = 4
+    ClientWidth = 203
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideTop.Control = tValueEdit
       AnchorSideTop.Side = asrCenter
@@ -118,9 +118,9 @@ object TProbForm: TTProbForm
       Left = 42
       Height = 15
       Top = 4
-      Width = 93
+      Width = 79
       Anchors = [akTop, akRight]
-      Caption = 'Student t value = '
+      Caption = 'Student t value'
       ParentColor = False
     end
     object tValueEdit: TEdit
@@ -128,7 +128,7 @@ object TProbForm: TTProbForm
       AnchorSideTop.Control = Panel1
       AnchorSideRight.Control = ProbEdit
       AnchorSideRight.Side = asrBottom
-      Left = 143
+      Left = 129
       Height = 23
       Top = 0
       Width = 74
@@ -145,9 +145,9 @@ object TProbForm: TTProbForm
       Left = 24
       Height = 15
       Top = 31
-      Width = 111
+      Width = 97
       Anchors = [akTop, akRight]
-      Caption = 'with deg. freedom = '
+      Caption = 'with deg. freedom'
       ParentColor = False
     end
     object DFEdit: TEdit
@@ -156,7 +156,7 @@ object TProbForm: TTProbForm
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = ProbEdit
       AnchorSideRight.Side = asrBottom
-      Left = 143
+      Left = 129
       Height = 23
       Top = 27
       Width = 74
@@ -173,8 +173,8 @@ object TProbForm: TTProbForm
       Left = 0
       Height = 15
       Top = 66
-      Width = 135
-      Caption = 'Probability larger value = '
+      Width = 121
+      Caption = 'Probability larger value'
       ParentColor = False
     end
     object ProbEdit: TEdit
@@ -182,7 +182,7 @@ object TProbForm: TTProbForm
       AnchorSideLeft.Side = asrBottom
       AnchorSideTop.Control = DFEdit
       AnchorSideTop.Side = asrBottom
-      Left = 143
+      Left = 129
       Height = 23
       Top = 62
       Width = 74
diff --git a/applications/lazstats/source/forms/simulations/tprobunit.pas b/applications/lazstats/source/forms/simulations/tprobunit.pas
index c91c679aa..7f2f97451 100644
--- a/applications/lazstats/source/forms/simulations/tprobunit.pas
+++ b/applications/lazstats/source/forms/simulations/tprobunit.pas
@@ -42,7 +42,7 @@ implementation
 {$R *.lfm}
 
 uses
-  Math, MathUnit;
+  Math, MathUnit, Utils;
 
 { TTProbForm }
 
@@ -54,18 +54,32 @@ begin
 end;
 
 procedure TTProbForm.ComputeBtnClick(Sender: TObject);
-VAR
-  tvalue, dfvalue, prob : double;
-  outvalue : string;
+var
+  tvalue, prob: double;
+  dfValue: Integer;
 begin
-  tvalue := StrToFloat(tValueEdit.Text);
-  dfvalue := StrToFloat(DFEdit.Text);
-  if tvalue >= 0.0 then prob := 0.5 * ProbT(tvalue,dfvalue);
-  if tvalue < 0.0 then prob :=  1.0 - ProbT(tvalue,dfvalue) +
-     (0.5 * probt(tvalue,dfvalue)) ;
-  if tvalue = 0.0 then prob := 0.50;
-  outvalue := format('%6.4f',[prob]);
-  ProbEdit.Text := outvalue;
+  if not MyTryStrToFloat(tValueEdit.Text, tvalue) then
+  begin
+    tValueEdit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+
+  if not TryStrToInt(DFEdit.Text, dfValue) then
+  begin
+    dfEdit.SetFocus;
+    ErrorMsg('Not a valid integer (must be positive).');
+    exit;
+  end;
+
+  if tvalue >= 0.0 then
+    prob := 0.5 * ProbT(tvalue, dfvalue)
+  else if tvalue < 0.0 then
+    prob :=  1.0 - ProbT(tvalue, dfvalue) + (0.5 *ProbT(tvalue, dfvalue))
+  else
+    prob := 0.50;
+
+  ProbEdit.Text := Format('%6.4f', [prob]);
 end;
 
 procedure TTProbForm.FormActivate(Sender: TObject);
diff --git a/applications/lazstats/source/forms/simulations/twozprobunit.lfm b/applications/lazstats/source/forms/simulations/twozprobunit.lfm
index e694e6cb4..7aadd1c3b 100644
--- a/applications/lazstats/source/forms/simulations/twozprobunit.lfm
+++ b/applications/lazstats/source/forms/simulations/twozprobunit.lfm
@@ -8,6 +8,7 @@ object TwozProbForm: TTwozProbForm
   Caption = 'Probability between two z scores'
   ClientHeight = 147
   ClientWidth = 378
+  OnActivate = FormActivate
   OnShow = ResetBtnClick
   Position = poMainFormCenter
   LCLVersion = '2.1.0.0'
@@ -15,25 +16,25 @@ object TwozProbForm: TTwozProbForm
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = ResetBtn
-    Left = 57
+    Left = 81
     Height = 25
     Top = 109
     Width = 62
     Anchors = [akTop, akRight]
     AutoSize = True
-    BorderSpacing.Left = 32
+    BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 12
     Cancel = True
     Caption = 'Cancel'
     ModalResult = 2
-    TabOrder = 0
+    TabOrder = 1
   end
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = ComputeBtn
-    Left = 131
+    Left = 155
     Height = 25
     Top = 109
     Width = 54
@@ -43,13 +44,13 @@ object TwozProbForm: TTwozProbForm
     BorderSpacing.Right = 12
     Caption = 'Reset'
     OnClick = ResetBtnClick
-    TabOrder = 1
+    TabOrder = 2
   end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = ReturnBtn
-    Left = 197
+    Left = 221
     Height = 25
     Top = 109
     Width = 76
@@ -59,25 +60,25 @@ object TwozProbForm: TTwozProbForm
     BorderSpacing.Right = 12
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 2
+    TabOrder = 3
   end
   object ReturnBtn: TButton
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = Owner
     AnchorSideRight.Side = asrBottom
-    Left = 285
+    Left = 309
     Height = 25
     Top = 109
     Width = 61
     Anchors = [akTop, akRight]
     AutoSize = True
     BorderSpacing.Top = 8
-    BorderSpacing.Right = 32
+    BorderSpacing.Right = 8
     BorderSpacing.Bottom = 8
     Caption = 'Return'
     ModalResult = 1
-    TabOrder = 3
+    TabOrder = 4
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -96,18 +97,18 @@ object TwozProbForm: TTwozProbForm
     AnchorSideLeft.Control = Owner
     AnchorSideLeft.Side = asrCenter
     AnchorSideTop.Control = Owner
-    Left = 74
+    Left = 81
     Height = 85
     Top = 8
-    Width = 231
+    Width = 217
     AutoSize = True
     BorderSpacing.Left = 8
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BevelOuter = bvNone
     ClientHeight = 85
-    ClientWidth = 231
-    TabOrder = 4
+    ClientWidth = 217
+    TabOrder = 0
     object Label1: TLabel
       AnchorSideLeft.Control = Panel1
       AnchorSideTop.Control = Z1Edit
@@ -115,15 +116,15 @@ object TwozProbForm: TTwozProbForm
       Left = 0
       Height = 15
       Top = 4
-      Width = 155
-      Caption = 'The probability between z1 = '
+      Width = 141
+      Caption = 'The probability between z1'
       ParentColor = False
     end
     object Z1Edit: TEdit
       AnchorSideLeft.Control = Label1
       AnchorSideLeft.Side = asrBottom
       AnchorSideTop.Control = Panel1
-      Left = 163
+      Left = 149
       Height = 23
       Top = 0
       Width = 68
@@ -137,12 +138,12 @@ object TwozProbForm: TTwozProbForm
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = Label1
       AnchorSideRight.Side = asrBottom
-      Left = 107
+      Left = 104
       Height = 15
       Top = 31
-      Width = 48
+      Width = 37
       Anchors = [akTop, akRight]
-      Caption = 'and z2 = '
+      Caption = 'and z2 '
       ParentColor = False
     end
     object Z2Edit: TEdit
@@ -151,7 +152,7 @@ object TwozProbForm: TTwozProbForm
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = Z1Edit
       AnchorSideRight.Side = asrBottom
-      Left = 163
+      Left = 149
       Height = 23
       Top = 27
       Width = 68
@@ -169,9 +170,9 @@ object TwozProbForm: TTwozProbForm
       Left = 84
       Height = 15
       Top = 66
-      Width = 71
+      Width = 57
       Anchors = [akTop, akRight]
-      Caption = 'Probability = '
+      Caption = 'Probability'
       ParentColor = False
     end
     object ProbEdit: TEdit
@@ -180,7 +181,7 @@ object TwozProbForm: TTwozProbForm
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = Z1Edit
       AnchorSideRight.Side = asrBottom
-      Left = 163
+      Left = 149
       Height = 23
       Top = 62
       Width = 68
diff --git a/applications/lazstats/source/forms/simulations/twozprobunit.pas b/applications/lazstats/source/forms/simulations/twozprobunit.pas
index e15d281a3..a82af24a2 100644
--- a/applications/lazstats/source/forms/simulations/twozprobunit.pas
+++ b/applications/lazstats/source/forms/simulations/twozprobunit.pas
@@ -6,8 +6,7 @@ interface
 
 uses
   Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
-  StdCtrls, ExtCtrls,
-  FunctionsLib;
+  StdCtrls, ExtCtrls;
 
 type
 
@@ -27,6 +26,7 @@ type
     Z1Edit: TEdit;
     Label1: TLabel;
     procedure ComputeBtnClick(Sender: TObject);
+    procedure FormActivate(Sender: TObject);
     procedure ResetBtnClick(Sender: TObject);
   private
     { private declarations }
@@ -39,6 +39,11 @@ var
 
 implementation
 
+{$R *.lfm}
+
+uses
+  Math, MathUnit, Utils;
+
 { TTwozProbForm }
 
 procedure TTwozProbForm.ResetBtnClick(Sender: TObject);
@@ -49,26 +54,37 @@ begin
 end;
 
 procedure TTwozProbForm.ComputeBtnClick(Sender: TObject);
-VAR
+var
   z1, z2, prob : double;
-  outvalue : string;
 begin
-     z1 := StrToFloat(Z1Edit.Text);
-     z2 := StrToFloat(Z2Edit.Text);
-     if z1 < z2 then
-     begin
-       prob := probz(z2) - probz(z1);
-     end;
-     if z1 > z2 then
-     begin
-       prob := probz(z1) - probz(z2);
-     end;
-     outvalue := format('%6.4f',[prob]);
-     ProbEdit.Text := outvalue;
+  if not MyTryStrToFloat(Z1Edit.Text, z1) then
+  begin
+    Z1Edit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+
+  if not MyTryStrToFloat(Z2Edit.Text, z2) then
+  begin
+    Z2Edit.SetFocus;
+    ErrorMsg('No valid number.');
+    exit;
+  end;
+
+  prob := abs(NormalDist(z2) - NormalDist(z1));
+  ProbEdit.Text := Format('%6.4f', [prob]);
 end;
 
-initialization
-  {$I twozprobunit.lrs}
+procedure TTwozProbForm.FormActivate(Sender: TObject);
+var
+  w: Integer;
+begin
+  w := MaxValue([CancelBtn.Width, ResetBtn.Width, ComputeBtn.Width, ReturnBtn.Width]);
+  CancelBtn.Constraints.MinWidth := w;
+  ResetBtn.Constraints.MinWidth := w;
+  ComputeBtn.Constraints.MinWidth := w;
+  ReturnBtn.Constraints.MinWidth := w;
+end;
 
 end.
 
diff --git a/applications/lazstats/source/units/mathunit.pas b/applications/lazstats/source/units/mathunit.pas
index 6abdc1a60..25ef944a1 100644
--- a/applications/lazstats/source/units/mathunit.pas
+++ b/applications/lazstats/source/units/mathunit.pas
@@ -46,6 +46,7 @@ function FactorialLn(n: Integer): Double;
 function PoissonPDF(n: integer; a: double): Double;
 function PoissonCDF(n: Integer; a: double): Double;
 
+function MyTryStrToFloat(S: String; out AValue: Double): Boolean;
 
 implementation
 
@@ -569,6 +570,20 @@ begin
 end;
 
 
+{ Converts a string to a floating point value. Checks for comma or point as
+  decimal separator }
+function MyTryStrToFloat(S: String; out AValue: Double): Boolean;
+var
+  fs: TFormatSettings;
+begin
+  Result := TryStrToFloat(S, AValue);
+  if not Result then
+  begin
+    fs := FormatSettings;
+    if fs.DecimalSeparator = '.' then fs.DecimalSeparator := ',' else fs.DecimalSeparator := '.';
+    Result := TryStrToFloat(S, AValue, fs);
+  end;
+end;
 
 initialization
   InitFactLn();
diff --git a/applications/lazstats/source/units/utils.pas b/applications/lazstats/source/units/utils.pas
index 7023d20d9..2380cb049 100644
--- a/applications/lazstats/source/units/utils.pas
+++ b/applications/lazstats/source/units/utils.pas
@@ -194,4 +194,3 @@ end;
 
 
 end.
-