Obtaining variances

As a reminder, to obtain variances by group (for the purpose of checking Fmax, for instance), you will want to follow these steps:

Choose "Data" from the menu across the top of SPSS.
From the Data drop-down menu, choose "Split File."
Click "Organize output by groups," and click over the name of your Grouping (or Independent or Between Subjects or Between Groups) variable.
Click "OK."
This will return you to the main screen, and sort your data into groups, which will each be analyzed separately.

Then choose "Analyze" from the menu across the top of SPSS.
From the Analyze drop-down menu, choose "Descriptive Statistics" and then "Frequencies."
Click over the name of your Outcome (or Response or Dependent) variable.
Uncheck the "Display frequency tables" box.
Click on "Statistics" and then choose "Variance." [While you're here, note that this is also where you would request "skew" or "kurtosis."]
Click "Continue."
Click "OK."

This will send you to an output screen, where your variances for the dependent variable will be listed by each level of the independent variable. From there, it is a simple step to pick out the largest variance and the smallest variance, and calculate Fmax.

Once you have done this, restore your data set to its original, unsplit condition by
Choose "Data" from the menu across the top of SPSS.
From the Data drop-down menu, choose "Split File."
Click "Analyze all cases, do not create groups."
Click "OK."
This will return you to the main screen.