Given the comparison of multiple groups, the Critical Mean Difference (CMD) is the minimum difference between any two of these group means that are significant at the given level of alpha. Four methods are available: Tukey, Bonferroni, Scheffe or unprotected t-tests.
Calculations
Tukey
Bonnferroni
Scheffe
t-test
Where:
- k is the number of Groups or Tests
- MSE is the Mean Square Error term
- n1 is the first group sample size
- n2 is the second group sample size
- Q is the Studentized Range Statistic
Menu
- File provides the ability Save or Print the output, or return to the Main Form.
- Edit allows Editing Output Text by cutting, copying, pasting, and undoing entry.
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- Help provides access to this Website.
Speed Buttons
These buttons provide quick access to the following tasks.
Returns to last Form or the Main Form.
Saves the output to a file.
Prints the Text.
Copies Selection to the clipboard.
Pastes Text from the clipboard
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Action Button
Performs calculations and displays output.
Output Text
The calculation output is displayed here when 
is clicked. You may save, print, edit, cut, copy, and paste text in this area.
is clicked. You may save, print, edit, cut, copy, and paste text in this area.Decimal Place Change
Changes the number of decimal places, from 0 to 9. Change may be made by selecting and typing in the number, or by using the incrementing buttons.
Alpha
Enter the level of Alpha here.
Groups
Enter the number of Groups in the comparison (or Tests for Bonferroni) here.
MSE
Enter the Mean-Square Error term here.
df(MSE)
Enter the Degrees of Freedom for the Mean-Square Error Term here.
n1
Enter the first sample size for one of the groups in the comparison here.
n2
Enter the second sample size for one of the groups in the comparison here.
Method Selection
Select Tukey, Bonferroni, Scheffe or t-test Critical Mean Differences to be calculated.