Irfan Ahmed, PhD

One-way within-subjects ANOVA A one-way within-subjects ANOVA allows you to determine if there is a relationship between a categorical IV and a continuous DV, where each subject is measured at every level of the IV. Within-subject ANOVA should be used whenever want to compare 3 or more groups where the same subjects are in all of the groups. To perform a within-subject ANOVA in SPSS you must have your data set organized so that the subject is the unit of analysis and you have different variables containing the value of the DV at each level of your within-subjects factor. To perform a within-subject ANOVA in SPSS: • Choose Analyze thenGoto General linear model thenGoto Repeated measures. • Type the name of the factor in the Within-Subjects Factor Name box. • Type the number of groups the factor represents in the Number of Levels box. • Click the Add button. • Click the Define button. • Move the variables representing the different levels of the within-subjects factor to the Wit...

Graphing Interactions in an ANOVA.   It is often useful to examine a plot of the means by condition when trying to interpret a significant interaction. To get plot of means by condition from SPSS • Perform a multifactor ANOVA as described above, but do not click the OK button to perform the analysis. • Click the Plots button. • Define all the plots you want to see. o To plot a main effect, move the factor to the Horizontal Axis box and click the Add button. o To plot a two-way interaction, move the first factor to the Horizontal Axis box, move the second factor to the Separate Lines box, and click the Add button. o To plot a three-way interaction, move the first factor to the Horizontal Axis box, move the second factor to the Separate Lines box, move the third factor to the Separate Plots box, and click the Add button. • Click the Continue button. • Click the OK button. In addition to the standard ANOVA output, the plots you requested will appear in a section titled Profile Plo...

SELECTING CASES in SPSS Sometimes a researcher may wish to restrict an analysis to only a subset of the data file. For example, a researcher might want to do an analysis on only the female participants, only on American citizens, or only on those who disagreed with a presented message. You can have SPSS only perform analyses on a subset of cases meeting specified criteria by selecting cases. For example, suppose you believed that an experimental manipulation would work better on female participants. You might therefore want to do an analysis only on the female participants. Assuming that you had a variable named gender in your data set where men had a value of 1 and women had a value of 2, you could select only women for analysis in SPSS by taking the following steps • Choose Data then Goto Select Cases. • Click the radio button next to If condition is satisfied . • Click the If button. • Type gender = 2 in the popup window. • Click the Continue button. • Click the OK button....