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# Two Way ANOVA In SPSS

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### Transcript of "Two Way ANOVA In SPSS"

1. 1. Two-Way ANOVA in SPSS <ul><li>Plan your analysis ahead of time </li></ul><ul><li>Select the same dependent variable </li></ul><ul><ul><li>Select two factors </li></ul></ul><ul><ul><li>Each factor is a nominal (grouping) variable </li></ul></ul><ul><ul><li>If both factors have many levels (values), your analysis will be complex </li></ul></ul><ul><li>SPSS will generate a lot of output. </li></ul><ul><li>Knowing which parts to use is important </li></ul>
2. 2. Set options to show Variable Names in Alphabetical Order Edit -> Options
3. 3. Use a boxplot to preview data Dependent variable Factor A Factor B
4. 4. Edited boxplot. Background changed to white. Text changed to white on outliers (doesn’t show) Notice that the labels for the variable names cut off in mid-sentence. If you edit the labels in Variable View, you can generate useful labels.
5. 5. Factorial ANOVA Analyze ->General Linear Model->Univariate
6. 6. Several steps to prepare: First: choose the variables DEPENDENT FACTOR A FACTOR B Notice that the buttons for options are vertically arranged along the side. Second, choose Options
7. 7. In the Options box … <ul><li>Request Means for Factors </li></ul><ul><li>Request Means for Interaction </li></ul><ul><li>Request descriptive statistics </li></ul><ul><li>Request estimates of effect size (This will generate an estimate of η 2 ) </li></ul><ul><li>Click CONTINUE </li></ul><ul><li>In main box, Click PLOTS </li></ul>
8. 8. Get a Plot of the Means of Groups <ul><li>Put Factor with the fewest categories into the box titled “Separate Lines” </li></ul><ul><li>Put other Factor into “Horizontal Axis” </li></ul><ul><li>Click on ADD to move variable names into the Plots listing box. </li></ul><ul><li>Click CONTINUE to return to main dialogue box. </li></ul><ul><li>Click POST HOC </li></ul>
9. 9. Choose Post-Hoc Tests <ul><li>Post-hoc tests are only needed if a Factor has a significant effect. You can request them now and decide later whether to use them. </li></ul><ul><li>Post-hoc tests are only needed if a factor has a significant effect AND if it has 3 or more groups </li></ul><ul><li>In this data, pricegas has 3 levels. Move pricegas to “Post hoc tests for” </li></ul><ul><li>Choose Scheff é test because groups are not equal size. </li></ul><ul><li>Note that Bonferroni (conservative) is also available. </li></ul><ul><li>Click CONTINUE for main dialogue box </li></ul>
10. 10. Click OK in the lower left corner
11. 11. Means of all groups Total = row or column means
12. 12. Hypothesis Test Results Factor A Factor B Interaction p -value η 2
13. 13. Post-hoc Tests All groups of pricegas differ from each other significantly
14. 14. Means Plot, Edited <ul><li>Background made white </li></ul><ul><li>Title on horizontal axis edited for clarity </li></ul><ul><li>Chart title deleted (APA format has Figure title below the chart) </li></ul><ul><li>Legend moved inside the box for clarity </li></ul>
15. 15. Write-up <ul><li>Sandwich format </li></ul><ul><li>Report three hypothesis tests with F and p- value for each: </li></ul><ul><ul><li>Factor A </li></ul></ul><ul><ul><li>Factor B </li></ul></ul><ul><ul><li>Interaction </li></ul></ul><ul><li>For any significant element, report means and effect size </li></ul><ul><li>For any significant element with 3 or more groups, report post-hoc tests </li></ul><ul><li>Close with a summary statement </li></ul><ul><li>Refer to boxplot or means plot as Figure 3 (or whichever number) in the write-up. </li></ul>
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