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Fisher

The Fisher strategy is used to perform all comparisons in pairs between the levels of a factor.

Example: We consider a data set with one factor and several levels, as in the following table.

Factor Fiber Strenght
15 7
15 7
15 15
15 11
15 9
20 12
20 17
20 12
20 18
20 18
25 14
25 18
25 18
25 19
25 19
30 19
30 25
30 22
30 19
30 23
35 7
35 10
35 11
35 15
35 11

click here to download the data

To use the tool Fisher the user must follow these steps: 

1. Access the menu:

Action $ \blacktriangleright $ ANOVA $ \blacktriangleright $ Multiple Comparisons $ \blacktriangleright $ Fisher


 

2. The following screen will be shown;

3. With the cursor in the field Factor select the column that refers to the Factor (without the name of the column).

4. With the cursor in the field Response Variable select the column that refers to the Response Variable (without the name of the column);

5. Choose the Significance Level α. In this case, we will use α = 0.05;

6. In Show Results, choose one of the options. We suggest the option New Sheet, because Action does not have the undo command;

7. To finish, click Ok.


Results and Interpretation

Once the process is finished, the following results will be shown:


As in the previous tests, we reject the equality between means of the levels if the p-value is < α or if the confidence interval does not conatin the value "zero". Thus, in the example, we reject the hypothesis of equality between level to all comparisons, except between levels 15 and 35, 20 and 25.