STATISTICA Basic Program: Post-HocsForFriedman.stb

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STATISTICA BASIC Program Post-HocsForFriedman.stb

{ This program performs nonparametric multiple comparisons. It uses the output from Friedman ANOVA by Ranks, either testing the Average Rank (in Column 1) or the Sum of Ranks (in Column 2). The test compares the absolute value of the differences for all pairs with a critical value which is determined using a normal approximation with suitable adjustment of alpha to take the multiple comparisons into account.

Program written, modified, or edited at StatSoft, Inc.}

if
DisplayMessageBox (MB_OKCANCEL, 'Nonparametric Multiple Comparisons',
	'This program runs on the Friedman ANOVA by Ranks results.  ' +
	'This must be the top Scrollsheet on the Screen')
= IDCANCEL then stop;

Friedman := GetScrollsheet (0);


{the formula can use either column in the output}

Test := DisplayButtonBox ('Which Type of Test', 'Average Rank|Sum of Ranks');
If Test = 0 then stop;

Alpha := 0.05;
if
DisplayNumericInputBox ('Significance Level', 'Please enter the overall significance level', Alpha)
= 0 then stop;


{get number of observations from the Scrollsheet}

ScrollsheetGetTitle (Friedman, 2, gettitle$);
ncases$ := Mid (gettitle$, 21, 6);
TheNCases := Val (ncases$);

{get number of groups from the Scrollsheet}

NumGroups := ScrollsheetGetNbRows (Friedman);

ReDim Diff(NumGroups,NumGroups);


{calculate the approximate Z-Score}

Z := Abs(VNormal (1-(Alpha/(NumGroups*(NumGroups-1))), 0, 1));

{calculate the correct critical value for the chosen test}

if Test = 1 then
	Critical := Z*Sqrt((NumGroups*(NumGroups+1))/(6*TheNCases))
else
	Critical := Z*Sqrt((TheNCases*NumGroups*(NumGroups+1))/6);

{loop through the comparisons}

for i := 1 to NumGroups-1 do
	for j := i+1 to NumGroups do begin
		ScrollsheetGetValue (Friedman, i, Test, Val1);
		ScrollsheetGetValue (Friedman, j, Test, Val2);
		Diff(i,j) := Abs(Val1-Val2);
		Diff(j,i) := Diff(i,j);
	end;


{get the titles for the Scrollsheet}

for i:= 1 to NumGroups do begin
	ScrollsheetGetRowName (Friedman, i, TempName$);
	FullNames$ := FullNames$ + TempName$;
	if i < NumGroups then FullNames$ := FullNames$ + '|';
end;

if Test = 1 then
	Title$ := 'Absolute Differences between Average Rank' +
		'|Approx. significant if > ' + str(Critical, 4, 2) +
		'|at ' + str (Alpha, 3, 2) + ' significance level'
else
	Title$ := 'Absolute Differences between Sum of Ranks' +
		'|Approx. significant if > ' + str(Critical, 4, 2) +
		'|at ' + str (Alpha, 3, 2) + ' significance level';


{create the Scrollsheet}

Results := NewScrollsheet (NumGroups, NumGroups, Diff, Title$, FullNames$, FullNames$);


{highlight the values above the critical value}

for i := 1 to NumGroups do
	for j := 1 to NumGroups do begin
		if Diff(i,j) > Critical then ScrollsheetSetHilite (Results, i, j, 1);
		if i = j then ScrollsheetSetTextValue (Results, i, j, '---');
	end;

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