diff --git a/applications/lazstats/docs/HelpNDoc/LazStats.hnd b/applications/lazstats/docs/HelpNDoc/LazStats.hnd
index c7adb2a95..8f5eb89e3 100644
Binary files a/applications/lazstats/docs/HelpNDoc/LazStats.hnd and b/applications/lazstats/docs/HelpNDoc/LazStats.hnd differ
diff --git a/applications/lazstats/docs/chm/LazStats.chm b/applications/lazstats/docs/chm/LazStats.chm
index 16397dfa9..be6575d71 100644
Binary files a/applications/lazstats/docs/chm/LazStats.chm and b/applications/lazstats/docs/chm/LazStats.chm differ
diff --git a/applications/lazstats/source/forms/simulations/distribunit.lfm b/applications/lazstats/source/forms/simulations/distribunit.lfm
index d4c24fe8b..4a6a5832d 100644
--- a/applications/lazstats/source/forms/simulations/distribunit.lfm
+++ b/applications/lazstats/source/forms/simulations/distribunit.lfm
@@ -1,13 +1,14 @@
 object DistribFrm: TDistribFrm
   Left = 420
-  Height = 301
+  Height = 223
   Top = 215
-  Width = 307
+  Width = 384
   AutoSize = True
   BorderStyle = bsDialog
   Caption = 'Distributions'
-  ClientHeight = 301
-  ClientWidth = 307
+  ClientHeight = 223
+  ClientWidth = 384
+  OnActivate = FormActivate
   OnCreate = FormCreate
   OnShow = FormShow
   Position = poMainFormCenter
@@ -32,7 +33,7 @@ object DistribFrm: TDistribFrm
     ClientHeight = 89
     ClientWidth = 176
     TabOrder = 0
-    object NDChk: TCheckBox
+    object NDChk: TRadioButton
       Left = 16
       Height = 19
       Top = 8
@@ -41,7 +42,7 @@ object DistribFrm: TDistribFrm
       OnClick = NDChkClick
       TabOrder = 0
     end
-    object ChiChk: TCheckBox
+    object ChiChk: TRadioButton
       Left = 16
       Height = 19
       Top = 35
@@ -50,7 +51,7 @@ object DistribFrm: TDistribFrm
       OnClick = ChiChkClick
       TabOrder = 1
     end
-    object FChk: TCheckBox
+    object FChk: TRadioButton
       Left = 16
       Height = 19
       Top = 62
@@ -61,29 +62,28 @@ object DistribFrm: TDistribFrm
     end
   end
   object GroupBox2: TGroupBox
-    AnchorSideLeft.Control = Owner
+    AnchorSideLeft.Control = GroupBox1
+    AnchorSideLeft.Side = asrBottom
     AnchorSideTop.Control = GroupBox1
-    AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = GroupBox1
     AnchorSideRight.Side = asrBottom
-    Left = 12
-    Height = 146
-    Top = 137
-    Width = 180
-    Anchors = [akTop, akLeft, akRight]
+    Left = 204
+    Height = 140
+    Top = 12
+    Width = 170
     AutoSize = True
     BorderSpacing.Left = 12
-    BorderSpacing.Top = 16
+    BorderSpacing.Right = 12
     BorderSpacing.Bottom = 12
     Caption = 'Parameters'
-    ClientHeight = 126
-    ClientWidth = 176
+    ClientHeight = 120
+    ClientWidth = 166
     TabOrder = 1
     object AlphaLabel: TLabel
       AnchorSideTop.Control = AlphaEdit
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = AlphaEdit
-      Left = 33
+      Left = 19
       Height = 15
       Top = 6
       Width = 84
@@ -92,57 +92,60 @@ object DistribFrm: TDistribFrm
       Caption = 'Type I Error Rate'
       ParentColor = False
     end
-    object Label2: TLabel
+    object DF1Label: TLabel
       AnchorSideTop.Control = DF1Edit
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = DF1Edit
-      Left = 26
+      Left = 12
       Height = 15
-      Top = 37
+      Top = 33
       Width = 91
       Anchors = [akTop, akRight]
       BorderSpacing.Right = 8
       Caption = 'Deg. Freedom (1)'
       ParentColor = False
     end
-    object Label3: TLabel
+    object DF2Label: TLabel
+      AnchorSideLeft.Control = GroupBox2
       AnchorSideTop.Control = DF2Edit
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = DF2Edit
-      Left = 26
+      Left = 12
       Height = 15
-      Top = 68
+      Top = 60
       Width = 91
-      Anchors = [akTop, akRight]
+      Anchors = [akTop, akLeft, akRight]
+      BorderSpacing.Left = 12
       BorderSpacing.Right = 8
       Caption = 'Deg. Freedom (2)'
       ParentColor = False
     end
-    object Label4: TLabel
+    object MeanLabel: TLabel
       AnchorSideTop.Control = MeanEdit
       AnchorSideTop.Side = asrCenter
       AnchorSideRight.Control = MeanEdit
-      Left = 87
+      Left = 73
       Height = 15
-      Top = 99
+      Top = 93
       Width = 30
       Anchors = [akTop, akRight]
       BorderSpacing.Right = 8
       Caption = 'Mean'
       ParentColor = False
+      Visible = False
     end
     object AlphaEdit: TEdit
       AnchorSideTop.Control = GroupBox2
       AnchorSideRight.Control = GroupBox2
       AnchorSideRight.Side = asrBottom
-      Left = 125
+      Left = 111
       Height = 23
       Top = 2
       Width = 43
       Alignment = taRightJustify
       Anchors = [akTop, akRight]
       BorderSpacing.Top = 2
-      BorderSpacing.Right = 8
+      BorderSpacing.Right = 12
       TabOrder = 0
       Text = 'AlphaEdit'
     end
@@ -151,130 +154,110 @@ object DistribFrm: TDistribFrm
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = AlphaEdit
       AnchorSideRight.Side = asrBottom
-      Left = 125
+      Left = 111
       Height = 23
-      Top = 33
+      Top = 29
       Width = 43
       Alignment = taRightJustify
       Anchors = [akTop, akRight]
-      BorderSpacing.Top = 8
+      BorderSpacing.Top = 4
       TabOrder = 1
-      Text = 'Edit1'
+      Text = 'DF1Edit'
     end
     object MeanEdit: TEdit
       AnchorSideTop.Control = DF2Edit
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = AlphaEdit
       AnchorSideRight.Side = asrBottom
-      Left = 125
+      Left = 111
       Height = 23
-      Top = 95
+      Top = 89
       Width = 43
       Alignment = taRightJustify
       Anchors = [akTop, akRight]
-      BorderSpacing.Top = 8
+      BorderSpacing.Top = 4
       BorderSpacing.Bottom = 8
       TabOrder = 3
-      Text = 'Edit1'
+      Text = 'MeanEdit'
+      Visible = False
     end
     object DF2Edit: TEdit
       AnchorSideTop.Control = DF1Edit
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = AlphaEdit
       AnchorSideRight.Side = asrBottom
-      Left = 125
+      Left = 111
       Height = 23
-      Top = 64
+      Top = 56
       Width = 43
       Alignment = taRightJustify
       Anchors = [akTop, akRight]
-      BorderSpacing.Top = 8
+      BorderSpacing.Top = 4
+      BorderSpacing.Bottom = 10
       TabOrder = 2
-      Text = 'Edit1'
+      Text = 'DF2Edit'
     end
   end
-  object Panel1: TPanel
-    AnchorSideLeft.Control = GroupBox1
-    AnchorSideLeft.Side = asrBottom
-    AnchorSideBottom.Control = GroupBox2
+  object CloseBtn: TButton
+    AnchorSideTop.Control = Bevel1
+    AnchorSideTop.Side = asrBottom
+    AnchorSideRight.Control = Owner
+    AnchorSideRight.Side = asrBottom
     AnchorSideBottom.Side = asrBottom
-    Left = 208
-    Height = 136
-    Top = 147
-    Width = 76
-    Anchors = [akLeft, akBottom]
+    Left = 321
+    Height = 25
+    Top = 180
+    Width = 55
+    Anchors = [akTop, akRight]
     AutoSize = True
-    BorderSpacing.Left = 16
-    BorderSpacing.Right = 12
-    BevelOuter = bvNone
-    ChildSizing.VerticalSpacing = 12
-    ClientHeight = 136
-    ClientWidth = 76
+    BorderSpacing.Top = 8
+    BorderSpacing.Right = 8
+    Caption = 'Close'
+    ModalResult = 11
+    TabOrder = 4
+  end
+  object ComputeBtn: TButton
+    AnchorSideTop.Control = CloseBtn
+    AnchorSideRight.Control = CloseBtn
+    Left = 237
+    Height = 25
+    Top = 180
+    Width = 76
+    Anchors = [akTop, akRight]
+    AutoSize = True
+    BorderSpacing.Left = 8
+    BorderSpacing.Right = 8
+    Caption = 'Compute'
+    OnClick = ComputeBtnClick
+    TabOrder = 3
+  end
+  object ResetBtn: TButton
+    AnchorSideTop.Control = CloseBtn
+    AnchorSideRight.Control = ComputeBtn
+    Left = 175
+    Height = 25
+    Top = 180
+    Width = 54
+    Anchors = [akTop, akRight]
+    AutoSize = True
+    BorderSpacing.Left = 8
+    BorderSpacing.Right = 8
+    BorderSpacing.Bottom = 8
+    Caption = 'Reset'
+    OnClick = ResetBtnClick
     TabOrder = 2
-    object ResetBtn: TButton
-      AnchorSideLeft.Control = Panel1
-      AnchorSideTop.Control = Panel1
-      AnchorSideRight.Control = Panel1
-      AnchorSideRight.Side = asrBottom
-      Left = 0
-      Height = 25
-      Top = 0
-      Width = 76
-      Anchors = [akTop, akLeft, akRight]
-      AutoSize = True
-      BorderSpacing.Bottom = 8
-      Caption = 'Reset'
-      OnClick = ResetBtnClick
-      TabOrder = 0
-    end
-    object CancelBtn: TButton
-      AnchorSideLeft.Control = Panel1
-      AnchorSideTop.Control = ResetBtn
-      AnchorSideTop.Side = asrBottom
-      AnchorSideRight.Control = Panel1
-      AnchorSideRight.Side = asrBottom
-      Left = 0
-      Height = 25
-      Top = 37
-      Width = 76
-      Anchors = [akTop, akLeft, akRight]
-      AutoSize = True
-      Caption = 'Cancel'
-      ModalResult = 2
-      TabOrder = 1
-    end
-    object ComputeBtn: TButton
-      AnchorSideLeft.Control = Panel1
-      AnchorSideTop.Control = CancelBtn
-      AnchorSideTop.Side = asrBottom
-      AnchorSideRight.Control = Panel1
-      AnchorSideRight.Side = asrBottom
-      Left = 0
-      Height = 25
-      Top = 74
-      Width = 76
-      Anchors = [akTop, akLeft, akRight]
-      AutoSize = True
-      Caption = 'Compute'
-      OnClick = ComputeBtnClick
-      TabOrder = 2
-    end
-    object ReturnBtn: TButton
-      AnchorSideLeft.Control = Panel1
-      AnchorSideTop.Control = ComputeBtn
-      AnchorSideTop.Side = asrBottom
-      AnchorSideRight.Control = Panel1
-      AnchorSideRight.Side = asrBottom
-      AnchorSideBottom.Side = asrBottom
-      Left = 0
-      Height = 25
-      Top = 111
-      Width = 76
-      Anchors = [akTop, akLeft, akRight]
-      AutoSize = True
-      Caption = 'Return'
-      ModalResult = 1
-      TabOrder = 3
-    end
+  end
+  object Bevel1: TBevel
+    AnchorSideLeft.Control = Owner
+    AnchorSideTop.Control = GroupBox2
+    AnchorSideTop.Side = asrBottom
+    AnchorSideRight.Control = Owner
+    AnchorSideRight.Side = asrBottom
+    Left = 0
+    Height = 8
+    Top = 164
+    Width = 384
+    Anchors = [akTop, akLeft, akRight]
+    Shape = bsBottomLine
   end
 end
diff --git a/applications/lazstats/source/forms/simulations/distribunit.pas b/applications/lazstats/source/forms/simulations/distribunit.pas
index 9fa5c8481..33ea1c5f6 100644
--- a/applications/lazstats/source/forms/simulations/distribunit.pas
+++ b/applications/lazstats/source/forms/simulations/distribunit.pas
@@ -1,3 +1,8 @@
+// Testing: no file needed
+//
+// Test input parameters:
+// - F distribution: DF1 = 3, DF2 = 20
+
 unit DistribUnit;
 
 {$mode objfpc}{$H+}
@@ -10,7 +15,7 @@ uses
   BlankFrmUnit, FunctionsLib, Globals;
 
   type
-    TwoCol = array[1..2,1..100] of double;
+    TwoCol = array[1..2, 1..100] of double;
 
 type
 
@@ -18,62 +23,48 @@ type
 
   TDistribFrm = class(TForm)
     AlphaEdit: TEdit;
+    Bevel1: TBevel;
+    ChiChk: TRadioButton;
     DF1Edit: TEdit;
     DF2Edit: TEdit;
+    FChk: TRadioButton;
     MeanEdit: TEdit;
-    Panel1: TPanel;
+    NDChk: TRadioButton;
     ResetBtn: TButton;
-    CancelBtn: TButton;
     ComputeBtn: TButton;
-    ReturnBtn: TButton;
+    CloseBtn: TButton;
     GroupBox2: TGroupBox;
     AlphaLabel: TLabel;
-    Label2: TLabel;
-    Label3: TLabel;
-    Label4: TLabel;
-    NDChk: TCheckBox;
-    ChiChk: TCheckBox;
-    FChk: TCheckBox;
+    DF1Label: TLabel;
+    DF2Label: TLabel;
+    MeanLabel: TLabel;
     GroupBox1: TGroupBox;
     procedure ChiChkClick(Sender: TObject);
     procedure ComputeBtnClick(Sender: TObject);
     procedure FChkClick(Sender: TObject);
+    procedure FormActivate(Sender: TObject);
     procedure FormCreate(Sender: TObject);
     procedure FormShow(Sender: TObject);
     procedure NDChkClick(Sender: TObject);
     procedure ResetBtnClick(Sender: TObject);
   private
     { private declarations }
-    procedure NDPlot(Sender : TObject);
-    procedure ChiPlot(Sender : TObject);
-    procedure FPlot(Sender : TObject);
-     procedure Hscale(Xmin, Xmax : double; Nsteps : integer;
-                 acolor : TColor; FontSize : integer;
-                 X, Y, Xlength : integer;
-                 charLabel : string; Sender : TObject);
-    procedure Vscale(Ymin, Ymax : double; Nsteps : integer;
-                 acolor : TColor; FontSize : integer;
-                 X, Y, Ylength : integer;
-                 charLabel : string; Sender : TObject);
-    procedure NormPts(zMin, zMax : double; Npts : integer;
-                  VAR realpts : TwoCol;
-                  Sender : TObject);
-    procedure PltPts(realpts : TwoCol;
-                   Xmax, Xmin, Ymax, Ymin : double;
-                   Npts, XaxisStart, YaxisStart, XaxisRange : integer;
-                   YaxisRange : integer;
-                   acolor : TColor; Sender : TObject);
-    procedure ChiPts(cMin, cMax : double;
-                             Npts, df : integer;
-                             VAR realpts : TwoCol;
-                             Sender : TObject);
-    procedure  FPts(FMin, FMax : double;
-                            Npts, df1, df2 : integer;
-                            VAR realpts : TwoCol;
-                            Sender : TObject);
-    function chi2func(chisqr, df : double) : double;
-    function Ffunc(F : double; df1, df2 : integer) : double;
+    procedure NDPlot;
+    procedure ChiPlot;
+    procedure FPlot;
+    procedure HScale(Xmin, Xmax: double; NSteps: integer; AColor: TColor;
+      FontSize: integer; X, Y, XLength: integer; CharLabel: string);
+    procedure VScale(Ymin, Ymax: double; NSteps: integer; AColor: TColor;
+      FontSize: integer; X, Y, YLength: integer; CharLabel: string);
+    procedure NormPts(zMin, zMax: double; NPts: integer; var RealPts: TwoCol);
+    procedure PltPts(RealPts: TwoCol; XMax, XMin, YMax, YMin: double;
+      Npts, XAxisStart, YAxisStart, XAxisRange, YAxisRange: integer; AColor: TColor);
+    procedure ChiPts(cMin, cMax: double; NPts, DF: integer; var RealPts: TwoCol);
+    procedure FPts(FMin, FMax: double; NPts, DF1, DF2: integer; var RealPts: TwoCol);
+    function Chi2Func(chisqr, df: double): double;
+    function FFunc(F: double; DF1, DF2: integer): double;
 
+    function Validate(out AMsg: String; out AControl: TWinControl): Boolean;
   public
     { public declarations }
   end; 
@@ -87,14 +78,14 @@ implementation
 
 procedure TDistribFrm.ResetBtnClick(Sender: TObject);
 begin
-     NDChk.Checked := false;
-     ChiChk.Checked := false;
-     FChk.Checked := false;
-     AlphaEdit.Text := '0.05';
-     DF1Edit.Text := '';
-     DF2Edit.Text := '';
-     MeanEdit.Text := '';
-     GroupBox2.Enabled := false;
+  NDChk.Checked := false;
+  ChiChk.Checked := false;
+  FChk.Checked := false;
+  AlphaEdit.Text := FormatFloat('0.00', DEFAULT_ALPHA_LEVEL);
+  DF1Edit.Text := '';
+  DF2Edit.Text := '';
+  MeanEdit.Text := '';
+  GroupBox2.Enabled := false;
 end;
 
 procedure TDistribFrm.FormShow(Sender: TObject);
@@ -110,9 +101,9 @@ begin
      AlphaLabel.Enabled := true;
      AlphaEdit.Enabled := true;
      DF1Edit.Enabled := false;
-     Label2.Enabled := false;
-     Label3.Enabled := false;
-     Label4.Enabled := false;
+     DF1Label.Enabled := false;
+     DF2Label.Enabled := false;
+     MeanLabel.Enabled := false;
      DF2Edit.Enabled := false;
      MeanEdit.Enabled := false;
    end
@@ -121,462 +112,471 @@ begin
 end;
 
 procedure TDistribFrm.ComputeBtnClick(Sender: TObject);
+var
+  msg: String;
+  C: TWinControl;
+  ok: Boolean;
 begin
-     if NDChk.Checked then
-     begin
-          NDPlot(self);
-     end;
-     if ChiChk.Checked then
-     begin
-          ChiPlot(self);
-     end;
-     if FChk.Checked then
-     begin
-          FPlot(self);
-     end;
+  if not Validate(msg, C) then
+  begin
+    C.SetFocus;
+    MessageDlg(msg, mtError, [mbOK], 0);
+    exit;
+  end;
+
+  ok := false;
+  if NDChk.Checked then
+  begin
+    NDPlot();
+    ok := true;
+  end;
+
+  if ChiChk.Checked then
+  begin
+    ChiPlot();
+    ok := true;
+  end;
+
+  if FChk.Checked then
+  begin
+    FPlot();
+    ok := true;
+  end;
+
+  if not ok then
+    MessageDlg('Please select a distribution.', mtError, [mbOK], 0);
 end;
 
 procedure TDistribFrm.FChkClick(Sender: TObject);
 begin
-     if FChk.Checked then
-     begin
-          GroupBox2.Enabled := true;
-          Label3.Enabled := true;
-          AlphaLabel.Enabled := true;
-          AlphaEdit.Enabled := true;
-          DF1Edit.Enabled := true;
-          DF2Edit.Enabled := true;
-          Label2.Enabled := true;
-          Label4.Enabled := false;
-          MeanEdit.Enabled := false;
-     end
-     else
-          GroupBox2.Enabled := false;
+  if FChk.Checked then
+  begin
+    GroupBox2.Enabled := true;
+    DF2Label.Enabled := true;
+    AlphaLabel.Enabled := true;
+    AlphaEdit.Enabled := true;
+    DF1Edit.Enabled := true;
+    DF2Edit.Enabled := true;
+    DF1Label.Enabled := true;
+    MeanLabel.Enabled := false;
+    MeanEdit.Enabled := false;
+  end
+  else
+    GroupBox2.Enabled := false;
 end;
 
 procedure TDistribFrm.ChiChkClick(Sender: TObject);
 begin
-     if ChiChk.Checked then
-     begin
-          GroupBox2.Enabled := true;
-          Label2.Enabled := true;
-          DF1Edit.Enabled := true;
-          Label3.Enabled := false;
-          Label4.Enabled := false;
-          AlphaLabel.Enabled := true;
-          AlphaEdit.Enabled := true;
-          DF2Edit.Enabled := false;
-          MeanEdit.Enabled := false;
-     end else
-          GroupBox2.Enabled := false;
+  if ChiChk.Checked then
+  begin
+    GroupBox2.Enabled := true;
+    DF1Label.Enabled := true;
+    DF1Edit.Enabled := true;
+    DF2Label.Enabled := false;
+    MeanLabel.Enabled := false;
+    AlphaLabel.Enabled := true;
+    AlphaEdit.Enabled := true;
+    DF2Edit.Enabled := false;
+    MeanEdit.Enabled := false;
+  end else
+    GroupBox2.Enabled := false;
 end;
 
-procedure TDistribFrm.NDPlot(Sender: TObject);
+procedure TDistribFrm.NDPlot;
 var
-   charLabel : string;
-   Clwidth, Clheight,X, Y, XaxisStart, XaxisEnd, YaxisStart, YaxisEnd : integer;
-   i, Xrange, Yrange, t : integer;
-   alpha, h, z, hprop, zprop : double;
-   realpts : TwoCol;
-
+  CharLabel: string;
+  Clwidth, Clheight,X, Y, XAxisStart, XAxisEnd, YAxisStart, YAxisEnd: integer;
+  i, Xrange, Yrange, t: integer;
+  alpha, h, z, hprop, zprop: double;
+  RealPts: TwoCol;
 begin
-     for i := 1 to 100 do realpts[1,i] := 0.0;
-     for i := 1 to 100 do realpts[2,i] := 0.0;
-     charLabel := 'Normal Distribution. Alpha = ';
-     BlankFrm.Image1.Canvas.Clear;
-     BlankFrm.Image1.Canvas.Pen.Color := clBlack;
-     BlankFrm.Image1.Canvas.Brush.Color := clWhite;
-     BlankFrm.Image1.Canvas.Clear;
-     BlankFrm.Image1.Canvas.FloodFill(1,1,clWhite,fsborder);
-     BlankFrm.Image1.Canvas.Pen.Width := 2;
-     Clwidth :=  BlankFrm.Image1.Width;
-     Clheight := BlankFrm.Image1.Height;
-     XaxisStart := Clwidth div 8;
-     XaxisEnd := Clwidth - (Clwidth div 8);
-     YaxisStart := (Clheight * 7) div 10;
-     YaxisEnd := Clheight div 10;
-     Xrange := XaxisEnd - XaxisStart;
-     Yrange := YaxisStart - YaxisEnd;
-     alpha := StrToFloat(AlphaEdit.Text);
-     BlankFrm.Show;
+  for i := 1 to 100 do realpts[1,i] := 0.0;
+  for i := 1 to 100 do realpts[2,i] := 0.0;
 
-     // Create values of normal curve
-     NormPts(-4.0, 4.0, 100, realpts, self);
-     PltPts(realpts, 4.0, -4.0, 0.5, 0.0, 100, XaxisStart, YaxisStart, Xrange,
-            Yrange, clBlack, self);
+  BlankFrm.Image1.Canvas.Pen.Color := clBlack;
+  BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+  BlankFrm.Image1.Canvas.Clear;
+  BlankFrm.Image1.Canvas.FloodFill(1,1,clWhite,fsborder);
+  BlankFrm.Image1.Canvas.Pen.Width := 2;
+  Clwidth :=  BlankFrm.Image1.Width;
+  Clheight := BlankFrm.Image1.Height;
 
-    // Draw line for alpha z := 1.645
-     charLabel := charLabel + AlphaEdit.Text;
-     BlankFrm.Caption := charLabel;
-     z := inversez(1.0 - alpha);
-     zprop := (4.0 + z) / 8.0;
-     h := (1.0 / sqrt(2.0 * 3.1415)) * (1.0 / exp(z * z / 2.0));
-     hprop := (0.5 - h) / 0.5;
-     X := round( zprop * Xrange)+ XaxisStart;
-     Y := YaxisEnd + round( hprop * Yrange);
-     BlankFrm.Image1.Canvas.MoveTo(X,YaxisStart);
-     BlankFrm.Image1.Canvas.LineTo(X,Y-10); // alpha cutoff
+  XAxisStart := Clwidth div 8;
+  XAxisEnd := Clwidth - Clwidth div 8;
+  YAxisStart := (Clheight * 7) div 10;
+  YAxisEnd := Clheight div 10;
+  XRange := XAxisEnd - XAxisStart;
+  YRange := YAxisStart - YAxisEnd;
+  alpha := StrToFloat(AlphaEdit.Text);
 
-     // floodfill rejection section with red
-     BlankFrm.Image1.Canvas.Brush.Color := clRed;
-     BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+  BlankFrm.Show;
 
-     // create labeled axis
-     Hscale(-4.0, 4.0, 11, clWhite, 10, XaxisStart, YaxisStart, Xrange,'z SCALE',self);
-     Vscale(0.0, 0.5, 11, clWhite, 10, XaxisStart, YaxisStart, Yrange, 'DENSITY',self);
+  // Create values of normal curve
+  NormPts(-4.0, 4.0, 100, RealPts);
+  PltPts(RealPts, 4.0, -4.0, 0.5, 0.0, 100, XAxisStart, YAxisStart, XRange, YRange, clBlack);
 
-     // Print Heading
-     t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
-     X := (BlankFrm.Width div 2) - (t div 2);
-     BlankFrm.Image1.Canvas.TextOut(X,0,charLabel);
-     charLabel := 'Critical Value = ';
-     charLabel := charLabel + format('%6.3f',[z]);
-     t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
-     X := (BlankFrm.Image1.Width div 2) - (t div 2);
-     BlankFrm.Image1.Canvas.TextOut(X,BlankFrm.Image1.Canvas.TextHeight(charLabel),charLabel);
+  // Draw line for alpha z := 1.645
+  CharLabel := 'Normal Distribution. Alpha: ' + AlphaEdit.Text;
+  BlankFrm.Caption := CharLabel;
+  z := inversez(1.0 - alpha);
+  zprop := (4.0 + z) / 8.0;
+  h := (1.0 / sqrt(2.0 * 3.1415)) * (1.0 / exp(z * z / 2.0));
+  hprop := (0.5 - h) / 0.5;
+  X := round(zprop * XRange) + XAxisStart;
+  Y := YAxisEnd + round(hprop * YRange);
+  BlankFrm.Image1.Canvas.MoveTo(X, YAxisStart);
+  BlankFrm.Image1.Canvas.LineTo(X, Y-10); // alpha cutoff
+
+  // floodfill rejection section with red
+  BlankFrm.Image1.Canvas.Brush.Color := clRed;
+  BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+
+  // create labeled axis
+  HScale(-4.0, 4.0, 11, clWhite, 10, XAxisStart, YAxisStart, XRange, 'z SCALE');
+  VScale(0.0, 0.5, 11, clWhite, 10, XAxisStart, YAxisStart, YRange, 'DENSITY');
+
+  // Print Heading
+  t := BlankFrm.Image1.Canvas.TextWidth(CharLabel);
+  X := (BlankFrm.Width - t) div 2;
+  BlankFrm.Image1.Canvas.TextOut(X, 0, charLabel);
+  CharLabel := 'Critical Value: ' + Format('%.3f',[z]);
+  t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
+  X := (BlankFrm.Image1.Width - t) div 2;
+  Y := BlankFrm.Image1.Canvas.TextHeight(CharLabel);
+  BlankFrm.Image1.Canvas.TextOut(X, Y, CharLabel);
 end;
 
-procedure TDistribFrm.ChiPlot(Sender: TObject);
+procedure TDistribFrm.ChiPlot;
 var
-   charLabel : string;
-   Clwidth, Clheight, X, Y, XaxisStart, XaxisEnd, YaxisStart, YaxisEnd : integer;
-   i, Xrange, Yrange, df, t : integer;
-   alpha, h, z, hprop, zprop, MaxChi, MaxProb : double;
-   realpts : TwoCol;
-
+  charLabel: string;
+  ClWidth, ClHeight, X, Y, XAxisStart, XAxisEnd, YAxisStart, YAxisEnd: integer;
+  i, Xrange, Yrange, df, t: integer;
+  alpha, h, z, hprop, zprop, MaxChi, MaxProb: double;
+  RealPts: TwoCol;
 begin
-     BlankFrm.Image1.Canvas.Clear;
-     for i := 1 to 100 do realpts[1,i] := 0.0;
-     for i := 1 to 100 do realpts[2,i] := 0.0;
-     charLabel := 'Chi Squared Distribution. Alpha = ';
-     MaxProb := 0.0;
-     BlankFrm.Image1.Canvas.Pen.Color := clBlack;
-     BlankFrm.Image1.Canvas.Brush.Color := clWhite;
-     BlankFrm.Image1.Canvas.Clear;
-     BlankFrm.Image1.Canvas.FloodFill(1,1,clWhite,fsborder);
-     BlankFrm.Image1.Canvas.Pen.Width := 2;
-     Clwidth :=  BlankFrm.Image1.Width;
-     Clheight := BlankFrm.Image1.Height;
-     XaxisStart := Clwidth div 8;
-     XaxisEnd := Clwidth - (Clwidth div 8);
-     YaxisStart := (Clheight * 7) div 10;
-     YaxisEnd := Clheight div 10;
-     Xrange := XaxisEnd - XaxisStart;
-     Yrange := YaxisStart - YaxisEnd;
-     alpha := StrToFloat(AlphaEdit.Text);
-     charLabel := charLabel + AlphaEdit.Text;
-     df := StrToInt(DF1Edit.Text);
-     if (df < 1) or (df > 100) then exit;
-     charLabel := charLabel + ' D.F. = ';
-     charLabel := charLabel + DF1Edit.Text;
-     BlankFrm.Caption := charLabel;
-     BlankFrm.Show;
+  for i := 1 to 100 do realpts[1,i] := 0.0;
+  for i := 1 to 100 do realpts[2,i] := 0.0;
 
-     // Create values of chi-squared curve
-     MaxChi := 125.0;
-     ChiPts(0.0, MaxChi, 100, df, realpts, self);
-     for i := 1 to 100 do
-     begin
-         if (realpts[2,i] > MaxProb) then MaxProb := realpts[2,i];
-     end;
-     PltPts(realpts, MaxChi, 0.0, MaxProb, 0.0, 100, XaxisStart, YaxisStart, Xrange,
-            Yrange, clBlack, self);
+  MaxProb := 0.0;
+  BlankFrm.Image1.Canvas.Pen.Color := clBlack;
+  BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+  BlankFrm.Image1.Canvas.Clear;
+  BlankFrm.Image1.Canvas.FloodFill(1, 1, clWhite, fsBorder);
+  BlankFrm.Image1.Canvas.Pen.Width := 2;
+  ClWidth :=  BlankFrm.Image1.Width;
+  ClHeight := BlankFrm.Image1.Height;
 
-    // Draw line for alpha
-     z := inversechi(1.0-alpha,df);
-     zprop := z / MaxChi;
-     h := chi2func(z,df);
-     hprop := (MaxProb - h) / MaxProb;
-     X := round( zprop * Xrange)+ XaxisStart;
-     Y := YaxisEnd + round( hprop * Yrange);
-     BlankFrm.Image1.Canvas.MoveTo(X,YaxisStart);
-     BlankFrm.Image1.Canvas.LineTo(X,Y); // alpha cutoff
+  XAxisStart := ClWidth div 8;
+  XAxisEnd := ClWidth - ClWidth div 8;
+  YAxisStart := (ClHeight * 7) div 10;
+  YAxisEnd := ClHeight div 10;
+  XRange := XAxisEnd - XAxisStart;
+  YRange := YAxisStart - YAxisEnd;
+  alpha := StrToFloat(AlphaEdit.Text);
+  charLabel := 'Chi Squared Distribution. Alpha: ' + AlphaEdit.Text;
+  df := StrToInt(DF1Edit.Text);
+  if (df < 1) or (df > 100) then
+    exit;
 
-     // floodfill main section with blue
-     BlankFrm.Image1.Canvas.Brush.Color := clBlue;
-     BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+  charLabel := charLabel + ' D.F.: ' + DF1Edit.Text;
+  BlankFrm.Caption := charLabel;
+  BlankFrm.Show;
 
-     // create charLabeled axis
-     Hscale(0.0, MaxChi, 11, clWhite, 10, XaxisStart, YaxisStart,
-        Xrange,'CHI SQUARED SCALE',self);
-     Vscale(0.0, MaxProb, 11, clWhite, 10, XaxisStart, YaxisStart,
-        Yrange, 'DENSITY',self);
+  // Create values of chi-squared curve
+  MaxChi := 125.0;
+  ChiPts(0.0, MaxChi, 100, df, realpts);
+  for i := 1 to 100 do
+    if (RealPts[2,i] > MaxProb) then
+      MaxProb := RealPts[2,i];
+  PltPts(RealPts, MaxChi, 0.0, MaxProb, 0.0, 100, XAxisStart, YAxisStart, XRange, YRange, clBlack);
 
-     // Print Heading
-     t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
-     X := (BlankFrm.Width div 2) - (t div 2);
-     BlankFrm.Image1.Canvas.TextOut(X,0,charLabel);
-     charLabel := 'Critical Value = ';
-     charLabel := charLabel + format('%6.3f',[z]);
-     t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
-     X := (BlankFrm.Image1.Width div 2) - (t div 2);
-     BlankFrm.Image1.Canvas.TextOut(X,BlankFrm.Image1.Canvas.TextHeight(charLabel),charLabel);
+  // Draw line for alpha
+  z := InverseChi(1.0-alpha, df);
+  zprop := z / MaxChi;
+  h := Chi2Func(z, df);
+  hprop := (MaxProb - h) / MaxProb;
+  X := round(zprop * Xrange) + XaxisStart;
+  Y := YaxisEnd + round(hprop * Yrange);
+  BlankFrm.Image1.Canvas.MoveTo(X, YaxisStart);
+  BlankFrm.Image1.Canvas.LineTo(X, Y); // alpha cutoff
+
+  // floodfill main section with blue
+  BlankFrm.Image1.Canvas.Brush.Color := clBlue;
+  BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+
+  // create charLabeled axis
+  HScale(0.0, MaxChi, 11, clWhite, 10, XAxisStart, YAxisStart, XRange, 'CHI SQUARED SCALE');
+  VScale(0.0, MaxProb, 11, clWhite, 10, XAxisStart, YAxisStart, YRange, 'DENSITY');
+
+  // Print Heading
+  t := BlankFrm.Image1.Canvas.TextWidth(CharLabel);
+  X := (BlankFrm.Width - t) div 2;
+  BlankFrm.Image1.Canvas.TextOut(X,0,CharLabel);
+
+  CharLabel := 'Critical Value: ' + Format('%6.3f',[z]);
+  t := BlankFrm.Image1.Canvas.TextWidth(CharLabel);
+  X := (BlankFrm.Image1.Width - t) div 2;
+  Y := BlankFrm.Image1.Canvas.TextHeight(CharLabel);
+  BlankFrm.Image1.Canvas.TextOut(X, Y, CharLabel);
 end;
 
-procedure TDistribFrm.FPlot(Sender: TObject);
+procedure TDistribFrm.FPlot;
 var
-     charLabel : string;
-     Clwidth, Clheight, X, Y, XaxisStart, XaxisEnd, YaxisStart, YaxisEnd : integer;
-     i, Xrange, Yrange, t, df1, df2 : integer;
-     realpts : TwoCol;
-     alpha, h, F, hprop, Fprop, MaxProb, MaxF : double;
-     done : boolean;
+  CharLabel: string;
+  ClWidth, ClHeight, X, Y, XAxisStart, XAxisEnd, YAxisStart, YAxisEnd: integer;
+  i, Xrange, Yrange, t, df1, df2: integer;
+  RealPts: TwoCol;
+  alpha, h, F, hprop, Fprop, MaxProb, MaxF: double;
+  done: boolean;
 begin
-     BlankFrm.Image1.Canvas.Clear;
-     for i := 1 to 100 do realpts[1,i] := 0.0;
-     for i := 1 to 100 do realpts[2,i] := 0.0;
-     MaxProb := 0.0;
-     charLabel := 'F Distribution. Alpha = ';
-     BlankFrm.Image1.Canvas.Pen.Color := clBlack;
-     BlankFrm.Image1.Canvas.Brush.Color := clWhite;
-     BlankFrm.Image1.Canvas.Clear;
-     BlankFrm.Image1.Canvas.FloodFill(1,1,clWhite,fsborder);
-     BlankFrm.Image1.Canvas.Pen.Width := 2;
-     Clwidth :=  BlankFrm.Image1.Width;
-     Clheight := BlankFrm.Image1.Height;
-     XaxisStart := Clwidth div 8;
-     XaxisEnd := Clwidth - (Clwidth div 8);
-     YaxisStart := (Clheight * 7) div 10;
-     YaxisEnd := Clheight div 10;
-     Xrange := XaxisEnd - XaxisStart;
-     Yrange := YaxisStart - YaxisEnd;
-     alpha := StrToFloat(AlphaEdit.Text);
-     charLabel := charLabel + AlphaEdit.Text;
-     df1 := StrToInt(DF1Edit.Text);
-     charLabel := charLabel + ' D.F.1 = ';
-     charLabel := charLabel + DF1Edit.Text;
-     df2 := StrToInt(DF2Edit.Text);
-     charLabel := charLabel + ' , D.F.2 = ';
-     charLabel := charLabel + DF2Edit.Text;
-     BlankFrm.Caption := charLabel;
-     BlankFrm.Show;
+  for i := 1 to 100 do
+  begin
+    realpts[1,i] := 0.0;
+    realpts[2,i] := 0.0;
+  end;
 
-     // Create values of F curve
-     MaxF := 20.0;
-     done := false;
-     while not done do
-     begin
-          h := Ffunc(MaxF, df1, df2);
-          if (h < 0.001)  then MaxF := MaxF - 1.0
-          else done := true;
-     end;
+  MaxProb := 0.0;
+  BlankFrm.Image1.Canvas.Pen.Color := clBlack;
+  BlankFrm.Image1.Canvas.Brush.Color := clWhite;
+  BlankFrm.Image1.Canvas.Clear;
+  BlankFrm.Image1.Canvas.FloodFill(1,1,clWhite,fsborder);
+  BlankFrm.Image1.Canvas.Pen.Width := 2;
+  ClWidth :=  BlankFrm.Image1.Width;
+  ClHeight := BlankFrm.Image1.Height;
+  XAxisStart := ClWidth div 8;
+  XAxisEnd := ClWidth - ClWidth div 8;
+  YAxisStart := (ClHeight * 7) div 10;
+  YAxisEnd := ClHeight div 10;
+  XRange := XAxisEnd - XAxisStart;
+  YRange := YAxisStart - YAxisEnd;
 
-     FPts(0.0, MaxF, 100, df1, df2, realpts, self);
-     for i := 1 to 100 do
-     begin
-         if (realpts[2,i] > MaxProb) then MaxProb := realpts[2,i];
-     end;
-     PltPts(realpts, MaxF, 0.0, MaxProb, 0.0, 100, XaxisStart, YaxisStart, Xrange,
-             Yrange, clBlack, self);
+  alpha := StrToFloat(AlphaEdit.Text);
+  charLabel := 'F Distribution. Alpha: ' + AlphaEdit.Text;
+  df1 := StrToInt(DF1Edit.Text);
+  CharLabel := CharLabel + ',  D.F.1: ';
+  CharLabel := CharLabel + DF1Edit.Text;
+  df2 := StrToInt(DF2Edit.Text);
+  CharLabel := CharLabel + ', D.F.2: ';
+  CharLabel := CharLabel + DF2Edit.Text;
+  BlankFrm.Caption := CharLabel;
+  BlankFrm.Show;
 
-     // Draw line for alpha
-     F := fpercentpoint(1.0-alpha,df1,df2);
-     Fprop := F / MaxF;
-     h := Ffunc(F,df1,df2);
-     hprop := (MaxProb - h) / MaxProb;
-     X := round( Fprop * Xrange)+ XaxisStart;
-     Y := YaxisEnd + round( hprop * Yrange);
-     BlankFrm.Image1.Canvas.MoveTo(X,YaxisStart);
-     BlankFrm.Image1.Canvas.LineTo(X,Y); // alpha cutoff
+  // Create values of F curve
+  MaxF := 20.0;
+  done := false;
+  while not done do
+  begin
+    h := Ffunc(MaxF, df1, df2);
+    if h < 0.001  then
+      MaxF := MaxF - 1.0
+    else
+      done := true;
+  end;
 
-     // floodfill main section with blue
-     BlankFrm.Canvas.Brush.Color := clBlue;
+  FPts(0.0, MaxF, 100, df1, df2, RealPts);
+  for i := 1 to 100 do
+    if (RealPts[2,i] > MaxProb) then
+      MaxProb := RealPts[2,i];
+  PltPts(RealPts, MaxF, 0.0, MaxProb, 0.0, 100, XAxisStart, YAxisStart, XRange, YRange, clBlack);
 
-     // create charLabeled axis
-     Hscale(0.0, MaxF, 11, clWhite, 10, XaxisStart, YaxisStart,
-        Xrange,'F SCALE',self);
-     Vscale(0.0, MaxProb, 11, clWhite, 10, XaxisStart, YaxisStart,
-        Yrange, 'DENSITY',self);
+  // Draw line for alpha
+  F := FPercentPoint(1.0-alpha, df1, df2);
+  Fprop := F / MaxF;
+  h := Ffunc(F, df1, df2);
+  hprop := (MaxProb - h) / MaxProb;
+  X := round(Fprop * XRange) + XAxisStart;
+  Y := YAxisEnd + round(hprop * YRange);
+  BlankFrm.Image1.Canvas.MoveTo(X, YAxisStart);
+  BlankFrm.Image1.Canvas.LineTo(X, Y); // alpha cutoff
 
-     // Print Heading
-     t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
-     X := (BlankFrm.Image1.Width div 2) - (t div 2);
-     BlankFrm.Image1.Canvas.TextOut(X,0,charLabel);
-     charLabel := 'Critical Value = ';
-     charLabel := charLabel + format('%6.3f',[F]);
-     t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
-     X := (BlankFrm.Image1.Width div 2) - (t div 2);
-     BlankFrm.Image1.Canvas.TextOut(X,BlankFrm.Image1.Canvas.TextHeight(charLabel),charLabel);
+  // floodfill main section with blue
+  BlankFrm.Canvas.Brush.Color := clBlue;
+
+  // create charLabeled axis
+  HScale(0.0, MaxF, 11, clWhite, 10, XAxisStart, YAxisStart, XRange, 'F SCALE');
+  VScale(0.0, MaxProb, 11, clWhite, 10, XAxisStart, YAxisStart, YRange, 'DENSITY');
+
+  // Print Heading
+  t := BlankFrm.Image1.Canvas.TextWidth(CharLabel);
+  X := (BlankFrm.Image1.Width - t) div 2;
+  BlankFrm.Image1.Canvas.TextOut(X, 0, CharLabel);
+  charLabel := 'Critical Value: ' + Format('%.3f', [F]);
+  t := BlankFrm.Image1.Canvas.TextWidth(charLabel);
+  X := (BlankFrm.Image1.Width - t) div 2;
+  Y := BlankFrm.Image1.Canvas.TextHeight(CharLabel);
+  BlankFrm.Image1.Canvas.TextOut(X, Y, CharLabel);
 end;
 
-procedure TDistribFrm.Hscale(Xmin, Xmax: double; Nsteps: integer;
-  acolor: TColor; FontSize: integer; X, Y, Xlength: integer; charLabel: string;
-  Sender: TObject);
+procedure TDistribFrm.HScale(XMin, XMax: double; Nsteps: integer;
+  AColor: TColor; FontSize: integer; X, Y, XLength: integer; CharLabel: string);
 var
-   i, TickEnd, Xpos, Ypos, TextX : integer;
-   Xincr, Xval : double;
-   Svalue, Ast : string;
+  i, TickEnd, Xpos, Ypos, TextX: integer;
+  Xincr, Xval: double;
 begin
-    BlankFrm.Image1.Canvas.MoveTo(X,Y);
-    BlankFrm.Image1.Canvas.LineTo(X+Xlength,Y);
-    BlankFrm.Image1.Canvas.Font.Size := FontSize;
-    BlankFrm.Image1.Canvas.Brush.Color := acolor;
-    TickEnd := Y + 10;
-    Xincr := (Xmax - Xmin) / Nsteps;
-    for i := 0 to Nsteps do
-    begin
-        Xpos := round(((Xlength / Nsteps) * i) + X);
-        BlankFrm.Image1.Canvas.MoveTo(Xpos,Y);
-        BlankFrm.Image1.Canvas.LineTo(Xpos,TickEnd);
-        TextX := Xpos - 8;
-        Xval := Xmin + ( i * Xincr);
-        Svalue := format('%4.2f',[Xval]);
-        Ast := Svalue;
-        BlankFrm.Image1.Canvas.TextOut(TextX, Y+15, Ast);
-    end;
-    // print charLabel below X axis
-    Ypos := Y + 30;
-    Xpos := round((BlankFrm.Width / 2) - (BlankFrm.Image1.Canvas.TextWidth(charLabel) / 2));
-    BlankFrm.Image1.Canvas.TextOut(Xpos,Ypos,charLabel);
+  BlankFrm.Image1.Canvas.MoveTo(X,Y);
+  BlankFrm.Image1.Canvas.LineTo(X+Xlength,Y);
+  BlankFrm.Image1.Canvas.Font.Size := FontSize;
+  BlankFrm.Image1.Canvas.Brush.Color := AColor;
+  TickEnd := Y + 10;
+  Xincr := (Xmax - Xmin) / Nsteps;
+  for i := 0 to Nsteps do
+  begin
+    XPos := round(Xlength/Nsteps*i + X);
+    BlankFrm.Image1.Canvas.MoveTo(XPos, Y);
+    BlankFrm.Image1.Canvas.LineTo(XPos, TickEnd);
+    TextX := XPos - 8;
+    Xval := Xmin + i*Xincr;
+    BlankFrm.Image1.Canvas.TextOut(TextX, Y+15, Format('%.2f', [Xval]));
+  end;
+
+  // print charLabel below X axis
+  YPos := Y + 30;
+  XPos := round((BlankFrm.Width / 2) - (BlankFrm.Image1.Canvas.TextWidth(CharLabel) / 2));
+  BlankFrm.Image1.Canvas.TextOut(Xpos, Ypos, CharLabel);
 end;
 
-procedure TDistribFrm.Vscale(Ymin, Ymax: double; Nsteps: integer;
-  acolor: TColor; FontSize: integer; X, Y, Ylength: integer; charLabel: string;
-  Sender: TObject);
+procedure TDistribFrm.VScale(YMin, YMax: double; NSteps: integer;
+  AColor: TColor; FontSize: integer; X, Y, YLength: integer; CharLabel: string);
 var
-   TickEnd, Ypos, Xpos, TextY : integer;
-   Yincr, Yval : double;
-   Svalue, symbol, Ast : string;
-   chpixs, i : integer;
+  TickEnd, Ypos, Xpos, TextY: integer;
+  Yincr, Yval: double;
+  chpixs, i: integer;
 begin
-    BlankFrm.Image1.Canvas.MoveTo(X,Y);
-    BlankFrm.Image1.Canvas.LineTo(X,Y-Ylength);
-    BlankFrm.Image1.Canvas.Font.Size := FontSize;
-    BlankFrm.Image1.Canvas.Brush.Color := acolor;
-    TickEnd := X - 10;
-    Yincr := (Ymax - Ymin) / Nsteps;
-    TextY := 0;
-    for i := 0 to Nsteps do
-    begin
-        Ypos := round(Y - ((Ylength / Nsteps) * i));
-        BlankFrm.Image1.Canvas.MoveTo(X,Ypos);
-        BlankFrm.Image1.Canvas.LineTo(TickEnd,Ypos);
-        TextY := TickEnd - 30;
-        Yval := Ymin + ( i * Yincr);
-        Svalue := format('%4.2f',[Yval]);
-        Ast := Svalue;
-        BlankFrm.Image1.Canvas.TextOut(TextY, Ypos-8, Ast);
-    end;
-    // print charLabel vertically
-    Xpos := TextY - 15;
-    for i := 1 to Length(charLabel) do
-    begin
-        chpixs := BlankFrm.Image1.Canvas.TextHeight(charLabel);
-        Ypos := round(Y - (Ylength / 2) - ( (Length(charLabel) * chpixs) / 2 ) + (chpixs * i));
-        symbol := charLabel[i];
-//        symbol[2] := 0;
-        BlankFrm.Image1.Canvas.TextOut(Xpos,Ypos,symbol);
-    end;
+  BlankFrm.Image1.Canvas.MoveTo(X,Y);
+  BlankFrm.Image1.Canvas.LineTo(X,Y-Ylength);
+  BlankFrm.Image1.Canvas.Font.Size := FontSize;
+  BlankFrm.Image1.Canvas.Brush.Color := AColor;
+
+  TickEnd := X - 10;
+  Yincr := (YMax - YMin) / Nsteps;
+  TextY := 0;
+  for i := 0 to NSteps do
+  begin
+    YPos := round(Y - Ylength / NSteps * i);
+    BlankFrm.Image1.Canvas.MoveTo(X, YPos);
+    BlankFrm.Image1.Canvas.LineTo(TickEnd, YPos);
+    TextY := TickEnd - 30;
+    Yval := Ymin + i * Yincr;
+    BlankFrm.Image1.Canvas.TextOut(TextY, Ypos-8, Format('%.2f', [Yval]));
+  end;
+
+  // print charLabel vertically
+  chpixs := BlankFrm.Image1.Canvas.TextHeight(CharLabel);
+  XPos := TextY - 15;
+  for i := 1 to Length(CharLabel) do
+  begin
+    YPos := round(Y - YLength / 2 - Length(charLabel) * chpixs / 2 + chpixs*i);
+    BlankFrm.Image1.Canvas.TextOut(XPos, YPos, CharLabel[i]);
+  end;
 end;
 
-procedure TDistribFrm.NormPts(zMin, zMax: double; Npts: integer;
-  var realpts: TwoCol; Sender: TObject);
+procedure TDistribFrm.NormPts(zMin, zMax: double; NPts: integer;
+  var RealPts: TwoCol);
 var
-   zIncr, z, h : double;
-   i : integer;
+  zIncr, z, h: double;
+  i: integer;
 begin
-     zIncr := (zMax - zMin) / Npts;
-     for i := 1 to Npts do
-     begin
-         z := zMin + (zIncr * i);
-         h := (1.0 / sqrt(2.0 * 3.14159265358979)) *
-              ( 1.0 / exp(z * z / 2.0));
-         realpts[1,i] := z;
-         realpts[2,i] := h;
-     end;
+  zIncr := (zMax - zMin) / Npts;
+  for i := 1 to Npts do
+  begin
+    z := zMin + (zIncr * i);
+    h := (1.0 / sqrt(2.0 * PI)) * (1.0 / exp(z * z / 2.0));
+    RealPts[1, i] := z;
+    RealPts[2, i] := h;
+  end;
 end;
 
-procedure TDistribFrm.PltPts(realpts: TwoCol; Xmax, Xmin, Ymax, Ymin: double;
-  Npts, XaxisStart, YaxisStart, XaxisRange: integer; YaxisRange: integer;
-  acolor: TColor; Sender: TObject);
+procedure TDistribFrm.PltPts(RealPts: TwoCol; Xmax, Xmin, Ymax, Ymin: double;
+  NPts, XAxisStart, YAxisStart, XAxisRange, YAxisRange: integer; AColor: TColor);
 var
-   hprop, zprop, z, h : double;
-   i, X, Y : integer;
-   intpts : array[1..100] of TPoint;
+  hprop, zprop, z, h: double;
+  i, X, Y: integer;
+  intpts: array[1..100] of TPoint;
 begin
-      for i := 1 to Npts do
-      begin
-          z := realpts[1,i];
-          h := realpts[2,i];
-          zprop := (z - Xmin) / (Xmax - Xmin);
-          X := round((zprop * XaxisRange) + XaxisStart);
-          hprop := (h - Ymin) / (Ymax - Ymin);
-          Y := round(YaxisStart - (hprop * YaxisRange));
-          intpts[i] := Point(X,Y);
-      end;
-      BlankFrm.Image1.Canvas.Pen.Color := acolor;
-      BlankFrm.Image1.Canvas.Polyline(Slice(intpts,Npts - 1));
+  for i := 1 to NPts do
+  begin
+    z := RealPts[1,i];
+    h := RealPts[2,i];
+    zprop := (z - XMin) / (XMax - XMin);
+    X := round(zprop * XAxisRange + XAxisStart);
+    hprop := (h - Ymin) / (Ymax - Ymin);
+    Y := round(YAxisStart - hprop * YAxisRange);
+    intpts[i] := Point(X, Y);
+  end;
+  BlankFrm.Image1.Canvas.Pen.Color := AColor;
+  BlankFrm.Image1.Canvas.Polyline(Slice(intpts, Npts - 1));
 end;
 
-procedure TDistribFrm.ChiPts(cMin, cMax: double; Npts, df: integer;
-  var realpts: TwoCol; Sender: TObject);
+procedure TDistribFrm.ChiPts(cMin, cMax: double; NPts, DF: integer;
+  var RealPts: TwoCol);
 var
-     ratio1, ratio2, ratio3, cIncr, chi, h : double;
-     i : integer;
+  ratio1, ratio2, ratio3, cIncr, chi, h: double;
+  i: integer;
 begin
-     ratio1 := df / 2.0;
-     ratio2 := (df - 2.0) / 2.0;
-     cIncr := (cMax - cMin) / Npts;
-     for i := 1 to Npts do
-     begin
-         chi := cMin + (cIncr * i);
+  ratio1 := DF / 2.0;
+  ratio2 := (DF - 2.0) / 2.0;
+  cIncr := (cMax - cMin) / NPts;
+  for i := 1 to NPts do
+  begin
+    chi := cMin + cIncr*i;
 //         h := inversechi(chi, df);
-         ratio3 := chi / 2.0;
-         h := (1.0 / (power(2.0,ratio1) * exp(lngamma(ratio1)))) * power(chi,ratio2) * ( 1.0 / exp(ratio3));
-         realpts[1,i] := chi;
-         realpts[2,i] := h;
-     end;
+    ratio3 := chi / 2.0;
+    h := (1.0 / (power(2.0, ratio1) * exp(lngamma(ratio1)))) * power(chi, ratio2) * (1.0 / exp(ratio3));
+    RealPts[1,i] := chi;
+    RealPts[2,i] := h;
+  end;
 end;
 
-procedure TDistribFrm.FPts(FMin, FMax: double; Npts, df1, df2: integer;
-  var realpts: TwoCol; Sender: TObject);
+procedure TDistribFrm.FPts(FMin, FMax: double; NPts, DF1, DF2: integer;
+  var RealPts: TwoCol);
 var
-     FIncr, F, h : double;
-     i : integer;
+  FIncr, F, h: double;
+  i: integer;
 begin
-     FIncr := (FMax - FMin) / Npts;
-     for i := 1 to Npts do
-     begin
-         F := FMin + (FIncr * i);
-         h := Ffunc(F, df1, df2);
-         realpts[1,i] := F;
-         realpts[2,i] := h;
-     end;
+  FIncr := (FMax - FMin) / NPts;
+  for i := 1 to NPts do
+  begin
+    F := FMin + FIncr * i;
+    h := Ffunc(F, DF1, DF2);
+    RealPts[1,i] := F;
+    RealPts[2,i] := h;
+  end;
 end;
 
-function TDistribFrm.chi2func(chisqr, df: double): double;
+function TDistribFrm.Chi2Func(ChiSqr, DF: double): double;
 var
-   ratio1, ratio2, ratio3, h : double;
+  ratio1, ratio2, ratio3: double;
 begin
-     // Returns the height of the density curve for the chi-squared statistic
-     ratio1 := df / 2.0;
-     ratio2 := (df - 2.0) / 2.0;
-     ratio3 := chisqr / 2.0;
-     h := (1.0 / (power(2.0,ratio1) * exp(lngamma(ratio1)))) * power(chisqr,ratio2) * ( 1.0 / exp(ratio3));
-     Result := h;
+  // Returns the height of the density curve for the chi-squared statistic
+  ratio1 := df / 2.0;
+  ratio2 := (df - 2.0) / 2.0;
+  ratio3 := chisqr / 2.0;
+  Result := (1.0 / (power(2.0,ratio1) * exp(lngamma(ratio1)))) * power(chisqr,ratio2) * (1.0 / exp(ratio3));
 end;
 
-function TDistribFrm.Ffunc(F: double; df1, df2: integer): double;
+function TDistribFrm.FFunc(F: double; DF1, DF2: integer): double;
 var
-   ratio1, ratio2, ratio3, ratio4, h : double;
-   part1, part2, part3, part4, part5, part6, part7, part8, part9 : double;
+  ratio1, ratio2, ratio3, ratio4: double;
+  part1, part2, part3, part4, part5, part6, part7, part8, part9: double;
 begin
-       // Returns the height of the density curve for the F statistic
-       ratio1 := (df1 + df2) / 2.0;
-       ratio2 := (df1 - 2.0) / 2.0;
-       ratio3 := df1 / 2.0;
-       ratio4 := df2 / 2.0;
-       part1 := exp(lngamma(ratio1));
-       part2 := power(df1,ratio3);
-       part3 := power(df2,ratio4);
-       part4 := exp(lngamma(ratio3));
-       part5 := exp(lngamma(ratio4));
-       part6 := power(F,ratio2);
-       part7 := power((F*df1+df2),ratio1);
-       part8 := (part1 * part2 * part3) / (part4 * part5);
-       if (part7 = 0.0) then part9 := 0.0
-       else part9 := part6 / part7;
-       h := part8 * part9;
+  // Returns the height of the density curve for the F statistic
+  ratio1 := (df1 + df2) / 2.0;
+  ratio2 := (df1 - 2.0) / 2.0;
+  ratio3 := df1 / 2.0;
+  ratio4 := df2 / 2.0;
+  part1 := exp(lngamma(ratio1));
+  part2 := power(df1, ratio3);
+  part3 := power(df2, ratio4);
+  part4 := exp(lngamma(ratio3));
+  part5 := exp(lngamma(ratio4));
+  part6 := power(F,ratio2);
+  part7 := power((F*df1 + df2), ratio1);
+  part8 := (part1 * part2 * part3) / (part4 * part5);
+  if (part7 = 0.0) then
+    part9 := 0.0
+  else
+    part9 := part6 / part7;
+  Result := part8 * part9;
 {
      ratio1 := (df1 + df2) / 2.0;
      ratio2 := (df1 - 2.0) / 2.0;
@@ -587,7 +587,16 @@ begin
               (gamma(ratio3) * gamma(ratio4))) *
               (realraise(f,ratio2) / realraise((f*df1+df2),ratio1));
 }
-       Result := h;
+end;
+
+procedure TDistribFrm.FormActivate(Sender: TObject);
+var
+  w: Integer;
+begin
+  w := MaxValue([ResetBtn.Width, ComputeBtn.Width, CloseBtn.Width]);
+  ResetBtn.Constraints.MinWidth := w;
+  ComputeBtn.Constraints.MinWidth := w;
+  CloseBtn.Constraints.MinWidth := w;
 end;
 
 procedure TDistribFrm.FormCreate(Sender: TObject);
@@ -596,6 +605,75 @@ begin
     Application.CreateForm(TBlankFrm, BlankFrm);
 end;
 
+function TDistribFrm.Validate(out AMsg: String; out AControl: TWinControl): boolean;
+var
+  x: Double;
+  n: Integer;
+begin
+  Result := false;
+  if AlphaEdit.Text = '' then
+  begin
+    AMsg := 'Input required.';
+    AControl := AlphaEdit;
+    exit;
+  end;
+  if not TryStrToFloat(AlphaEdit.Text, x) or (x <= 0) or (x >= 1.0) then
+  begin
+    AMsg := 'Numerical value between 0 and 1 required.';
+    AControl := AlphaEdit;
+    exit;
+  end;
+
+  if ChiChk.Checked or FChk.Checked then
+  begin
+    if DF1Edit.Text = '' then
+    begin
+      AMsg := 'Input required.';
+      AControl := DF1Edit;
+      exit;
+    end;
+    if not TryStrToInt(DF1Edit.Text, n) or (n <= 0) then
+    begin
+      AMsg := 'Positive numerical value required.';
+      AControl := DF1Edit;
+      exit;
+    end;
+  end;
+
+  if FChk.Checked then
+  begin
+    if DF2Edit.Text = '' then
+    begin
+      AMsg := 'Input required.';
+      AControl := DF2Edit;
+      exit;
+    end;
+    if not TryStrToInt(DF2Edit.Text, n) or (n <= 0) then
+    begin
+      AMsg := 'Positive numerical value required.';
+      AControl := DF2Edit;
+      exit;
+    end;
+  end;
+
+  (*
+  if MeanEdit.Text = '' then
+  begin
+    AMsg := 'Input required.';
+    AControl := MeanEdit;
+    exit;
+  end;
+  if not TryStrToFloat(MeanEdit.Text, x) then
+  begin
+    AMsg := 'Numerical value required.';
+    AControl := MeanEdit;
+    exit;
+  end;
+  *)
+
+  Result := true;
+end;
+
 initialization
   {$I distribunit.lrs}