unit KR21Unit;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
  StdCtrls;

type

  { TKR21Frm }

  TKR21Frm = class(TForm)
    ResetBtn: TButton;
    CancelBtn: TButton;
    ComputeBtn: TButton;
    ReturnBtn: TButton;
    NoItemsEdit: TEdit;
    MeanEdit: TEdit;
    StdDevEdit: TEdit;
    RelEdit: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    procedure ComputeBtnClick(Sender: TObject);
    procedure FormShow(Sender: TObject);
    procedure ResetBtnClick(Sender: TObject);
  private
    { private declarations }
  public
    { public declarations }
  end; 

var
  KR21Frm: TKR21Frm;

implementation

{ TKR21Frm }

procedure TKR21Frm.ResetBtnClick(Sender: TObject);
begin
     NoItemsEdit.Text := '';
     MeanEdit.Text := '';
     StdDevEdit.Text := '';
     RelEdit.Text := '';
end;

procedure TKR21Frm.FormShow(Sender: TObject);
begin
     ResetBtnClick(self);
end;

procedure TKR21Frm.ComputeBtnClick(Sender: TObject);
var
   items, mean, stddev, rel : double;
begin
     items := StrToFloat(NoItemsEdit.Text);
     mean := StrToFloat(MeanEdit.Text);
     stddev := StrToFloat(StdDevEdit.Text);
     rel := (items / (items - 1.0)) * (1.0 - (mean * (items - mean))/
          (items * sqr(stddev)));
     RelEdit.Text := FloatToStr(rel);
end;

initialization
  {$I kr21unit.lrs}

end.