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Changeset 9329

Timestamp:

03/21/13 13:26:16 (11 years ago)

Author:

ascheibe

Message:

#1886 calculate Cohen's D and Hedges' G for pairwise comparison and updated documentation

Location:

Files:

-                      r9328
+                      r9329
     /// <returns>Cohen's d.
     /// d = 0.2 means small effect
     /// d = 0.5 means average effect
+    /// d = 0.5 means medium effect
     /// d = 0.8 means big effect
     /// According to Wikipedia this means: "A lower Cohen's d indicates a necessity of larger sample sizes, and vice versa."
     /// </returns>
     public static double CohensD(double[] d1, double[] d2) {
+    public static double CalculateCohensD(double[] d1, double[] d2) {
       double x1, x2, s1, s2;
 …
     /// <summary>
+    /// Calculates Hedges' g.
+    /// Calculates Hedges' g.
+    /// Hedges' g works like Cohen's d but corrects for bias.
     /// </summary>
     /// <returns>Hedges' g</returns>
     public static double HedgesG(double[] d1, double[] d2) {
+    public static double CalculateHedgesG(double[] d1, double[] d2) {
       double x1, x2, s1, s2, n1, n2, s, g, c;

-                      r9320
+                      r9329
 using System.Windows.Forms;
 using HeuristicLab.Analysis.AlgorithmBehavior.Analyzers;
+using HeuristicLab.Analysis.AlgorithmBehavior.Analyzers.Views;
 using HeuristicLab.Core.Views;
 using HeuristicLab.Data;
 …
       DoubleMatrix pValsMatrix = new DoubleMatrix(1, stringConvertibleMatrixView.Content.Columns);
       pValsMatrix.ColumnNames = stringConvertibleMatrixView.Content.ColumnNames;
       pValsMatrix.RowNames = new string[] { "p-Values" };
+      pValsMatrix.RowNames = new string[] { "p-Value" };
       double val;
 …
+      }
       DoubleMatrix pValsMatrix = new DoubleMatrix(1, stringConvertibleMatrixView.Content.Columns);
+      DoubleMatrix pValsMatrix = new DoubleMatrix(3, stringConvertibleMatrixView.Content.Columns);
       pValsMatrix.ColumnNames = stringConvertibleMatrixView.Content.ColumnNames;
       pValsMatrix.RowNames = new string[] { "p-Values" };
+      pValsMatrix.RowNames = new string[] { "p-Value", "Cohen's d", "Hedges' g" };
       double bothtails;
 …
         alglib.mannwhitneyutest(data[colIndex], data[colIndex].Length, data[i], data[i].Length, out bothtails, out lefttail, out righttail);
         pValsMatrix[0, i] = bothtails;
+        pValsMatrix[1, i] = SampleSizeDetermination.CalculateCohensD(data[colIndex], data[i]);
+        pValsMatrix[2, i] = SampleSizeDetermination.CalculateHedgesG(data[colIndex], data[i]);
+      }

-                      r9320
+                      r9329
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         f65+ofviu18cf+mbWTUz/pL/cuHX4lfyr468Xva6e9Z/9vGb5Dfzc4Vv5d8efcd41/s+7P3EfOYH7IeK
         j3ofuz55f3q4kLyw8Bv3hPP74uYdwgAAAAlwSFlzAAALDwAACw8BkvkDpQAAABl0RVh0U29mdHdhcmUA
+        j3ofuz55f3q4kLyw8Bv3hPP74uYdwgAAAAlwSFlzAAALDgAACw4BQL7hQQAAABl0RVh0U29mdHdhcmUA
         UGFpbnQuTkVUIHYzLjUuODc7gF0AAAK0SURBVDhPrZBrSNNRAMWNvkVEEBT0oY+BUAgSRBhIQmUqKYb4
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 …
 For pairwise comparision of the groups the Mann-Whitney U test is used.
+It also requires sample sizes of at least 5 samples.</value>
+It also requires sample sizes of at least 5 samples.
+The p-values calculated by the statistical tests are interpreted as follows:
+The null hypothesis states that the groups which are compared have the same distribution.
+A p-value &lt; 0.05 (this value is often chosen as significance level)  means the null hypothesis is rejected,
+which therefore means that the distributions are not equal.
+For the pariwise statistical test, in addition to the p-value, Cohen's d and Hedges' g are calculated.
+According to Wikipedia, these values can be interpreted as follows: "A lower Cohen's d indicates a necessity of larger sample sizes, and vice versa."</value>
   </data>
 </root>

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