diff --git a/applications/lazstats/LazStats.chm b/applications/lazstats/LazStats.chm
index b689e5937..7597c8d28 100644
Binary files a/applications/lazstats/LazStats.chm and b/applications/lazstats/LazStats.chm differ
diff --git a/applications/lazstats/docs/HelpNDoc/LazStats.hnd b/applications/lazstats/docs/HelpNDoc/LazStats.hnd
index 0bd97e09f..313f0fbe6 100644
Binary files a/applications/lazstats/docs/HelpNDoc/LazStats.hnd and b/applications/lazstats/docs/HelpNDoc/LazStats.hnd differ
diff --git a/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.lfm b/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.lfm
index 6480b03d9..465a423fc 100644
--- a/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.lfm
+++ b/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.lfm
@@ -1,12 +1,14 @@
 object RelChangeFrm: TRelChangeFrm
   Left = 855
-  Height = 163
+  Height = 190
   Top = 410
   Width = 400
+  HelpType = htKeyword
+  HelpKeyword = 'ReliabilityduetoTestVarianceChan.htm'
   AutoSize = True
-  BorderStyle = bsSingle
-  Caption = 'Variance Change Affect on Reliability'
-  ClientHeight = 163
+  BorderStyle = bsDialog
+  Caption = 'Variance Change Effect on Reliability'
+  ClientHeight = 190
   ClientWidth = 400
   OnActivate = FormActivate
   OnShow = FormShow
@@ -15,10 +17,10 @@ object RelChangeFrm: TRelChangeFrm
   object ResetBtn: TButton
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
-    AnchorSideRight.Control = CancelBtn
-    Left = 103
+    AnchorSideRight.Control = ComputeBtn
+    Left = 183
     Height = 25
-    Top = 128
+    Top = 148
     Width = 54
     Anchors = [akTop, akRight]
     AutoSize = True
@@ -30,31 +32,13 @@ object RelChangeFrm: TRelChangeFrm
     OnClick = ResetBtnClick
     TabOrder = 2
   end
-  object CancelBtn: TButton
-    AnchorSideTop.Control = Bevel1
-    AnchorSideTop.Side = asrBottom
-    AnchorSideRight.Control = ComputeBtn
-    Left = 169
-    Height = 25
-    Top = 128
-    Width = 62
-    Anchors = [akTop, akRight]
-    AutoSize = True
-    BorderSpacing.Left = 12
-    BorderSpacing.Top = 8
-    BorderSpacing.Right = 12
-    BorderSpacing.Bottom = 8
-    Caption = 'Cancel'
-    ModalResult = 2
-    TabOrder = 3
-  end
   object ComputeBtn: TButton
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
-    AnchorSideRight.Control = ReturnBtn
-    Left = 243
+    AnchorSideRight.Control = CloseBtn
+    Left = 249
     Height = 25
-    Top = 128
+    Top = 148
     Width = 76
     Anchors = [akTop, akRight]
     AutoSize = True
@@ -64,35 +48,35 @@ object RelChangeFrm: TRelChangeFrm
     BorderSpacing.Bottom = 8
     Caption = 'Compute'
     OnClick = ComputeBtnClick
-    TabOrder = 4
+    TabOrder = 3
   end
-  object ReturnBtn: TButton
+  object CloseBtn: TButton
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = Owner
     AnchorSideRight.Side = asrBottom
-    Left = 331
+    Left = 337
     Height = 25
-    Top = 128
-    Width = 61
+    Top = 148
+    Width = 55
     Anchors = [akTop, akRight]
     AutoSize = True
     BorderSpacing.Left = 12
     BorderSpacing.Top = 8
     BorderSpacing.Right = 8
     BorderSpacing.Bottom = 8
-    Caption = 'Return'
-    ModalResult = 1
-    TabOrder = 5
+    Caption = 'Close'
+    ModalResult = 11
+    TabOrder = 4
   end
   object HelpBtn: TButton
     Tag = 142
     AnchorSideTop.Control = Bevel1
     AnchorSideTop.Side = asrBottom
     AnchorSideRight.Control = ResetBtn
-    Left = 40
+    Left = 120
     Height = 25
-    Top = 128
+    Top = 148
     Width = 51
     Anchors = [akTop, akRight]
     AutoSize = True
@@ -109,15 +93,16 @@ object RelChangeFrm: TRelChangeFrm
     AnchorSideLeft.Side = asrCenter
     AnchorSideTop.Control = Owner
     Left = 51
-    Height = 104
+    Height = 116
     Top = 8
     Width = 299
     AutoSize = True
-    BorderSpacing.Left = 8
+    BorderSpacing.Left = 16
     BorderSpacing.Top = 8
-    BorderSpacing.Right = 8
+    BorderSpacing.Right = 16
+    BorderSpacing.Bottom = 8
     BevelOuter = bvNone
-    ClientHeight = 104
+    ClientHeight = 116
     ClientWidth = 299
     TabOrder = 0
     object Label1: TLabel
@@ -165,7 +150,7 @@ object RelChangeFrm: TRelChangeFrm
       AnchorSideRight.Control = NewRelEdit
       Left = 0
       Height = 15
-      Top = 85
+      Top = 97
       Width = 218
       Anchors = [akTop, akRight]
       BorderSpacing.Right = 8
@@ -219,23 +204,35 @@ object RelChangeFrm: TRelChangeFrm
     end
     object NewRelEdit: TEdit
       AnchorSideLeft.Control = OldRelEdit
-      AnchorSideTop.Control = NewVarEdit
+      AnchorSideTop.Control = Bevel2
       AnchorSideTop.Side = asrBottom
       AnchorSideRight.Control = Panel1
       AnchorSideRight.Side = asrBottom
       Left = 226
       Height = 23
-      Top = 81
+      Top = 93
       Width = 73
       Alignment = taRightJustify
       Anchors = [akTop, akLeft, akRight]
-      BorderSpacing.Top = 4
+      BorderSpacing.Top = 8
       Font.Style = [fsBold]
       ParentFont = False
       ReadOnly = True
       TabOrder = 3
       Text = 'Edit1'
     end
+    object Bevel2: TBevel
+      AnchorSideLeft.Control = Panel1
+      AnchorSideTop.Control = NewVarEdit
+      AnchorSideTop.Side = asrBottom
+      AnchorSideRight.Side = asrBottom
+      Left = 0
+      Height = 8
+      Top = 77
+      Width = 400
+      Anchors = [akTop, akLeft, akRight]
+      Shape = bsBottomLine
+    end
   end
   object Bevel1: TBevel
     AnchorSideLeft.Control = Owner
@@ -245,7 +242,7 @@ object RelChangeFrm: TRelChangeFrm
     AnchorSideRight.Side = asrBottom
     Left = 0
     Height = 8
-    Top = 112
+    Top = 132
     Width = 400
     Anchors = [akTop, akLeft, akRight]
     Shape = bsBottomLine
diff --git a/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.pas b/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.pas
index 64ef27ec6..97b1b32ed 100644
--- a/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.pas
+++ b/applications/lazstats/source/forms/analysis/measurement_programs/relchangeunit.pas
@@ -15,12 +15,12 @@ type
 
   TRelChangeFrm = class(TForm)
     Bevel1: TBevel;
+    Bevel2: TBevel;
     HelpBtn: TButton;
     Panel1: TPanel;
     ResetBtn: TButton;
-    CancelBtn: TButton;
     ComputeBtn: TButton;
-    ReturnBtn: TButton;
+    CloseBtn: TButton;
     OldRelEdit: TEdit;
     OldVarEdit: TEdit;
     NewVarEdit: TEdit;
@@ -53,10 +53,10 @@ uses
 
 procedure TRelChangeFrm.ResetBtnClick(Sender: TObject);
 begin
-     OldRelEdit.Text := '';
-     NewRelEdit.Text := '';
-     OldVarEdit.Text := '';
-     NewVarEdit.Text := '';
+  OldRelEdit.Text := '';
+  NewRelEdit.Text := '';
+  OldVarEdit.Text := '';
+  NewVarEdit.Text := '';
 end;
 
 procedure TRelChangeFrm.FormActivate(Sender: TObject);
@@ -66,12 +66,11 @@ begin
   if FAutoSized then
     exit;
 
-  w := MaxValue([HelpBtn.Width, ResetBtn.Width, CancelBtn.Width, ComputeBtn.Width, ReturnBtn.Width]);
+  w := MaxValue([HelpBtn.Width, ResetBtn.Width, ComputeBtn.Width, CloseBtn.Width]);
   HelpBtn.Constraints.MinWidth := w;
   ResetBtn.Constraints.MinWidth := w;
-  CancelBtn.Constraints.MinWidth := w;
   ComputeBtn.Constraints.MinWidth := w;
-  ReturnBtn.Constraints.MinWidth := w;
+  CloseBtn.Constraints.MinWidth := w;
 
   Constraints.MinHeight := Height;
   Constraints.MaxHeight := Height;
@@ -93,13 +92,28 @@ end;
 
 procedure TRelChangeFrm.ComputeBtnClick(Sender: TObject);
 var
-   OldRel, NewRel, OldVar, NewVar : double;
+  oldRel, newRel, oldVar, newVar: double;
 begin
-     OldRel := StrToFloat(OldRelEdit.Text);
-     OldVar := StrToFloat(OldVarEdit.Text);
-     NewVar := StrToFloat(NewVarEdit.Text);
-     NewRel := 1.0 - ((OldVar / NewVar) * (1.0 - OldRel));
-     NewRelEdit.Text := FormatFloat('0.00000', NewRel);  //FloatToStr(NewRel);
+  if (OldRelEdit.Text = '') or not TryStrToFloat(OldRelEdit.Text, oldRel) then
+  begin
+    OldRelEdit.SetFocus;
+    MessageDlg('Valid number required.', mtError, [mbOK], 0);
+    exit;
+  end;
+  if (OldVarEdit.Text = '') or not TryStrToFloat(OldVarEdit.Text, oldVar) then
+  begin
+    OldVarEdit.SetFocus;
+    MessageDlg('Valid number required.', mtError, [mbOK], 0);
+    exit;
+  end;
+  if (NewVarEdit.Text = '') or not TryStrToFloat(NewVarEdit.Text, newVar) then
+  begin
+    NewVarEdit.SetFocus;
+    MessageDlg('Valid number required.', mtError, [mbOK], 0);
+    exit;
+  end;
+  newRel := 1.0 - (oldVar / newVar) * (1.0 - oldRel);
+  NewRelEdit.Text := FormatFloat('0.00000', newRel);
 end;