• If you choose to do this, you must pay attention to the level of analysis inherent in that file.
  • The states file contains data on people in the aggregate--it reports what proportion of all votes went to Bush.
  • Sociology uses the term ecology for the study of groups
  • So this type of data is known in social research as ecological data.
• Because the states file has observations on states, not on individual voters, you will be explaining the voting behavior of states, not voters.
  • Accordingly, you can make statements like the following:
    • The correlation between percent black and percent vote for Reagan in 1984 across all American states was -.56, which indicates that 31% of the variance in the states' votes for Reagan can be explained by the racial composition of the state.
  • From the same correlation, you cannot make this statement:
    • -- which indicates that 31% of the variance in voting choice for Reagan can be explained by the racial characteristics of American voters.
• If you make such a statement, you are committing an ecological fallacy--making an unsupported generalization from group data to individual behavior.
• If you wish to predict the voting behavior of individual citizens, you must use survey data on individual respondents, such as
  • vote00
  • vote96
  • vote92
  • vote88

Consider this set of [ecological] data for three communities:	r = 1.00
Community % Republican vote % over $50,000 A 25 25 B 50 50 C 75 75   Observing that r=1.0, one might be tempted to draw this erroneous conclusion: There is a perfect relationship between making over $50,000 and voting Republican.

---

In truth, the correlation between wealth and Republican vote for individuals
in the same three communities could have been r=-.33

Consider three separate samples of 100 voters taken in each community:

Community A	Community B	Community C
voted Rep voted Dem Under $50,000   25 75 50 75% Over $50,000 25 0   25 25% 25% 75%	voted Rep voted Dem Under $50,000   50 50 0 50% Over $50,000 50 0   50 50% 50% 50%	voted Rep voted Dem Under $50,000   25 25 0 25% Over $50,000 75 50   25 75% 75% 25%

Now let's combine the three samples into one, looking at only the survey data for individuals: