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Most mean comparison tests do not use LSD value to identify means
that are statistically different.
Many mean comparison tests have been designed by statisticians. ARM
includes LSD, Duncan's MRT (called Duncan's New Multiple Range Test),
Student-Newman-Keuls, Tukey's, Waller-Duncan, and Dunnett's. Mean
comparisons based on LSD have often been criticized because the
significance level "slips" when the number of treatments increases.
If a group of treatment means are sorted into order from high to low,
then Duncan's and LSD give approximately the same result for adjacent
pairs of treatment means. With Duncan's and Student-Newman-Keuls, the
minimum value for significance becomes larger for mean pairs that are
further apart in the sorted list. Both LSD and Tukey's use the same
value for all tests, but the Tukey's value is quite large when compared
to the LSD. (Thus, there are fewer significant differences.)
To use LSD as the mean comparison test (or to change mean comparison
method, then:
1. Select File - Print Reports from the ARM menu bar.
2. Double-click on the Summary heading in the left available reports
column to expand the list of available summary reports.
3. Click on AOV Means Table in the left column so this choice is
highlighted.
4. Click the Edit Report Options button at bottom right of Print
Reports dialog to display AOV Means Table report 0ptions.
5. Click the down pointing arrow following the mean comparison test
method. Select LSD to use this test method, or try another test method.
6. Click the Help button for more information on mean comparison
tests. |
