Exercise 3. Personal financial situation and presidential vote
Many observers claimed that the condition of the nation's economy would be a factor affecting how people voted in the 2004 presidential election. This is not surprising. In past elections, the feelings that voters had about the economy were an important influence on their voting behavior. To examine this relationship for 2004, you should start by generating a table that shows how an individual's assessment of his or her personal financial situation over the past year (V062) was related to the individual's presidential vote. For the reasons suggested in Exercise 1, you should use the recoded version of V002 that you created for that exercise, so that you examine only the major-party vote (i.e., only the Bush and Kerry voters).
Table 3A raises the question of exactly how and why feelings about the economy influence presidential voting. We can explore how such feelings affect voting by examining possible intervening variables. Intervening variables are those that are influenced by the independent variable and in turn affect the dependent variable. Intervening variables are the linkage through which one variable affects another. In this case, we might examine voter assessments of how Bush had handled the economy as a potential intervening variable (V058).
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. This will produce a separate subtable for each category of the intervening variable. In order to ensure that we have a sufficient number of respondents in each column of each subtable, it may be necessary to recode the variables. In this exercise, you should recode V062 so that there are just three categories (better, same, and worse), and you should recode V058 so that there are just two categories (approve and disapprove). This will make the three-variable table easier to interpret.
In this example, the relationship between personal financial situation and presidential vote is extremely weak once we control for assessment of Bush's handling of the economy. This tells us that whatever effect that personal financial situation has on presidential vote is due largely to the effect that personal financial situation has on how the voter assesses the president's handling of the economy. If the original two-variable relationship had basically remained as strong in the three-variable table, then we would conclude that the control variable was not an intervening variable in this relationship.