Exercise 6: Gender and congressional vote
One of the interesting features of American politics over the past 20-25 years is the existence of a gender gap in voting behavior. Specifically, women have been more likely than men to vote for Democratic candidates. To examine this relationship for 2008, you should generate a table that shows how an individual's gender (V168) was related to the individual's congressional vote. For the reasons suggested in exercise 2, you should use the recoded version of V003 that you created for that exercise, so that you examine only the major-party vote for the U.S. House.
Table 6A raises as many questions as it answers. Why should gender be related to the vote? What explains the greater tendency for women to vote Democratic (or men to vote Republican)? We can attempt to explain this relationship by examining possible intervening variables (i.e., those that are influenced by the independent variable and in turn affect the dependent variable). In this case, we would might want to identify the attitudes that create a gender gap in voting. Some people might speculate that attitudes toward abortion produce the relationship. Democrats have usually been more supportive of abortion rights than have Republicans. Perhaps women were more likely to vote for Democratic House candidates because they were more supportive of abortion and cast their ballots on the basis of that issue.
As we saw in exercise 5, in order to examine a potential intervening variable, you should run the original two-variable relationship with the potential intervening variable added as a control variable. In this exercise, you should use V104 (attitude toward abortion) as your control variable, and you should recode V104 so that there are just two categories (favor and oppose), which will make the three-variable table easier to interpret. For information on how to create a three-variable table using SDA, see exercises 3 or 4.
In this example, the relationship between gender and congressional vote is just as strong when we control for abortion attitude as it is when we do not. This tells us that the effect that gender has on congressional vote is not due to attitudes on abortion. If the original two-variable relationship had largely disappeared in the three-variable table (which is what happened in exercise 5), then we would have concluded that the control variable was a key intervening variable in this relationship, but that is not what happened.