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One of the most common questions I hear is how to enter and analyze data from a two by two crosstabulation. It is not immediately obvious, especially to beginners, how to get started with this type of data. This is part 5 of a series of 6 handouts on this topic (view handouts 1, 2, 3, 4, 6). There is also a video version of this topic. Part 5 explains how to produce a crosstabulation and calculate an odds ratio.
Select ANALYZE | DESCRIPTIVE STATISTICS | CROSSTABS from the menu.
Add "Risk.Factor" to the ROW(S) field and "Outcome" to the COLUMN(S) field.
When you click on the STATISTICS button, you will see the dialog box shown above. Click on the RISK option and then on the CONTINUE button.
When you click on the CELLS button, you will see the dialog box shown above. Click on the ROW PERCENTAGES option and the click on the CONTINUE button, then the OK button.
Compare the table produced by CROSSTABS (shown above) to the table you had laid out earlier (shown below).
I did this deliberately to get you comfortable with the fact that PASW/SPSS has to make assumptions about displaying the data, and those assumptions may or may not be exactly what you want. PASW/SPSS decided to arrange the table in order of the numeric codes. If you dislike that order, you can always go back and change the numeric codes. I would encourage you instead to embrace the ambiguity and get comfortable with alternate ways of displaying the same data set.
The table shown above, produced because we selected the RISK option, informs you that the odds ratio is 0.8. In this particular example, the relative risks (0.884 and 1.110) are not appropriate measures of risk because this is a case control design.