11.3 Running One-way ANOVA

Open your ezdata.sav file and select Analyze, Compare Means, One-Way ANOVA... from the menu (Figure 11.1).

A One-Way ANOVA dialog window will appear. Select Leader Performance 1 (perform1) on the left and move it to the Dependent List: pane on the right. Next scroll all the way down on the left, select Sex Role Type (sextype) and move it to the Factor: pane on the lower right. Note that SPSS uses the term, Factor, to refer to the independent variable, so these terms are synonymous. This will generate the ANOVA table when we run the analysis. But recall that we need to specify the multiple comparisons of group means first, so to do this click the Post Hoc... button at the bottom.

A One-Way ANOVA: Post Hoc Multiple Comparisons window will appear (Figure 11.3). There are numerous statistical procedures one can choose from to perform these comparisons, but a discussion of these is beyond the scope of this chapter. For our purposes, select the LSD box. LSD stands for Least Significant Difference.

Briefly, a value is computed which is how much two means must differ to justify rejecting Ho and concluding they are significantly different. The differences between all possible pairs of means are computed by subtraction. These mean differences are compared to the Least Significant Difference value. Any two means that differ at least by this amount will be judged to be significantly different at the .05 level.

Click the Continue button at the bottom of this window and SPSS will return to the original One-Way ANOVA dialog window. Next we need to specify what other statistics besides the F-value that we want to compute. To do this, click the Options... button at the bottom of this window (Figure 11.4).

A One-Way ANOVA: Options dialog window will appear (Figure 11.5). Researchers typically want to examine descriptive statistics, so check the Descriptive box. Researchers also typically select the Homogeneity of variance test as well to determine whether or not this condition of ANOVA has been met. However, to simplify this example, we will not perform this test here. Last, recall that a visual depiction of results can greatly facilitate intepretation, so check the Means plot box. Then click the Continue button.

This will return you to the main dialog window. To run the ANOVA, click the OK button in the upper right corner.