SPSSv15_interaction_BarGraph - Graphing an Interaction in...

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Graphing an Interaction in SPSS version 15: BAR GRAPH There is a good chance that sometime during your career you will be asked to graph an interaction. Briefly defined, an interaction is when the effect of one independent variable on the dependent variable depends on the different levels of one or more other independent variables. We will practice graphing an interaction from a 2 x 2 between-subjects factorial design. Step 1. Click on Graphs , then Legacy Dialogs and select Bar . Step 2. In the Bar Charts menu, click on Clustered and then make sure Summaries for groups of cases is selected (this is the default option). Then click “ Define .” Step 3. In the Define Cluster Bar menu, first select Other statistic (e.g., mean) that enables you to plot the means of your groups, and then select your dependent variable measure (e.g., “guilty”) and move it into the Variable field. The default will be to compute the mean for that variable. Step 4. Now move the one of the independent variables (e.g., " sex ") into the Category Axis field. Then, move the other independent variable (e.g., “ cond ”) into the Define Clusters by field. The category axis variable will be the variable that appears along the horizontal axis. The define clusters by variable will represent the other IV that has a legend. Note: This figure is constructed as a bar graph because the variable in the categorical axis is a discrete variable; this is how I was trained. If that variable was continuous, then creating a line graph would be more appropriate. Others may feel that a line graph is always more desirable, while others have no preference, so check with your professor or colleagues.
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