Contents
- Index
Tab 6: Group - Analysis
Tab 6 of the Test Distribution window displays the results of several analyses to detect differences between groups. In order for these analyses to be performed, the group column must be filled out in the Data window. A plot of the data by group is displayed on Tab 5: Group - Plot. If significant differences between the groups are detected, this tab will be bolded in the Test Distribution window. Any significant differences are highlighted in red.
The following analyses are performed:
Group Averages Different: The first analysis performed is an Analysis of Variance (ANOVA) to see if the averages of the groups are different. This analysis assumes the data within the groups fits the normal distribution and that the standard deviations are equal. The p-value and confidence level are reported. A significant difference is reported if the p-value is less than or equal to 0.05 and the results are highlighted in red.
Group Medians Different: The second analysis performed is the Kruskall-Wallis test to see if the medians of the groups are different. This is a nonparametric test that makes no assumptions about the distributions of the groups. It is an alternative to the above ANOVA. The p-value and confidence level are reported. A significant difference is reported if the p-value is less than or equal to 0.05 and the results are highlighted in red.
Group Standard Deviations Different: The third analysis performed is the Levene's test to see if the standard deviations of the groups are different. This analysis assumes the data within the groups fits the normal distribution. The p-value and confidence level are reported. A significant difference is reported if the p-value is less than or equal to 0.05 and the results are highlighted in red.
Comparison of Averages: The average of each group is displayed along with 95% confidence intervals. This analysis assumes the data within the groups fits the normal distribution and that the standard deviations are equal. If the ANOVA or Kruskall-Wallis test is significant, this section can be used to further compare the group averages. A Tukey-Kramer Multiple Comparison is also performed to determine which groups are significantly different. For each group, there is a corresponding column with a "+" sign in it. Any other groups with "x" signs in the same column are significantly different. Above, group 1 is significantly different from groups 3 and 4 but is not significantly different than group 2.
Comparison of Standard Deviations: The standard deviation of each group is displayed along with 95% confidence intervals. These confidence intervals assume the data within the groups fits the normal distribution. If Levene's test is significant, this section can be used to further compare the group standard deviations.
By performing a right mouse click over the graphic or clicking the Menu button, the following popup menu will appear:
The menu items are as follows:
Size To Fit: Sizes output to fit window. Output will shrink and expand to fit window when window is resized.
Fixed Size - Normal: Sizes output so easy to read. If the output is too large to fit the window, scroll bars are added.
Fixed Size - Custom: Can specify the size of the output. If the output is too large to fit the window, scroll bars are added.
Print: Prints the output.
Copy to Clipboard: Copies the output to the clipboard in Windows Meta file (Picture) format.