STATISTICA Basic Program: Post-HocsForKruskal.stb

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STATISTICA BASIC Program Post-HocsForKruskal.stb

{ This program performs nonparametric multiple comparisons. It uses the output from the Scrollsheet headed "Kruskal-Wallis ANOVA by Ranks" in the Kruskal-Wallis ANOVA and Median Test analysis. The test compares the absolute value of the differences in mean ranks 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.}

RandomAccess;
NoDataFileVariableNames;


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

Kruskal := GetScrollsheet(0);

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


{get number of groups from the Scrollsheet}

NumGroups := ScrollsheetGetNbRows (Kruskal);


ReDim Diff(NumGroups,NumGroups);
ReDim Test(NumGroups,NumGroups);
ReDim ValN(NumGroups);


{calculate the approximate Z-score}

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

ScrollsheetGetMatrix (Kruskal, 1, 2, ValN);
ValSum (ValN, 1, NumGroups, NumTotal);


{calculate the constant part of the critical value}

AlwaysSame := Z*Sqrt((NumTotal*(NumTotal+1))/12);


{loop through the comparisons}

for i := 1 to NumGroups-1 do
	for j := 1+i to NumGroups do begin

		ScrollsheetGetValue (Kruskal, i, 3, Sum1);
		ScrollsheetGetValue (Kruskal, i, 2, Num1);
		ScrollsheetGetValue (Kruskal, j, 3, Sum2);
		ScrollsheetGetValue (Kruskal, j, 2, Num2);

		Diff(i,j) := Abs((Sum1/Num1) - (Sum2/Num2));
		Diff(j,i) := Diff(i,j);


		{create the critical value depending upon sample sizes}

		If Diff(i,j) > AlwaysSame*Sqrt((1/Num1)+(1/Num2))
			then Test(i,j) := 1 else Test(i,j) := 0;
		Test(j,i) := Test(i,j);
	end;


{get Scrollsheet titles}

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

Title$ := 'Absolute Differences between Mean Rank' +
	'|Approx. significant if highlighted ' +
	'|at ' + str (Alpha, 3, 2) + ' significance level';


{create Scrollsheet}

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


{highlight those above the critical value}

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

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