The key issue is to correct for experiment-wise error. We also describe the Scheffé test, which can be used for non-pairwise comparisons. Where the variances are unequal we can also use the Brown-Forsythe F* Test. Fisher’s LSD, Student Newman-Keuls (SNK) and Tukey’s B) are not very accurate and usually should not be used. These tests are designed only for pairwise comparisons (i.e. We also describe extensions to Tukey’s HSD test (Tukey-Kramer and Games and Howell) where the sample sizes or variances are unequal.We can also use the Real Statistics function QCRIT(4,44,.05,2, FALSE), as described below, to get the same result of 3.7775.
One continues in this manner until no subsets remain to be tested.
First we arrange the sample means in descending order There are three tables in Figure 7.
Enter Ctrl-m and select Single Factor Anova and Follow-up Tests from the menu.
Enter A3: D15 in the Input Range, check Column headings included with data, select the Tukey HSD option and click on OK. A better alternative to Tukey-Kramer when variances are unequal is Games and Howell.
The test can also be used when the group means are not equal via although, since Dunnett’s Table is based on equal group sizes, the above formula is only accurate if the group sizes are not too different.
Real Statistics Function: The following function is provided in the Real Statistics Resource Pack: DCRIT( = TRUE (default) harmonic interpolation is used; otherwise linear interpolation is used.
= TRUE (default) harmonic interpolation is used; otherwise linear interpolation is used.
This function is based on the table of critical values provided in Studentized Range q Table.
The table in the upper left hand side of the figure consists of the variables sorted from highest to lowest mean. rank) of these variables, where = 4 refers to the variable with lowest mean (i.e. The table in the upper right side of the figure is used to determine the critical values of mean differences.
These are based on the possible values of in that column.
This means that there is a significant difference between women who take the drug and men in the control (first column) and there is also a significant difference between women who take the drug and women in the control.