The 1910 California Gubernatorial Primary

Topics Addressed

1. Estimation of Proportions
2. Political Science

In 1910, a man named Hiram Johnson entered the California gubernatorial primary. For each county in the state, data are available giving the percentage of native-born Americans in the county and the percentage of the vote for Johnson, but no data exist on the individual voter level relating native-born versus immigrant status to preference for or against Johnson. Two political scientists writing in a book in 1970 calculated the correlation between the county-level percentages, and got +0.5. They used this number to measure the extent to which Johnson received native, as opposed to immigrant, support in the election.

Is the correlation they calculated a fair measure of this, or does it seem too high or too low as an indication of the relationship at the individual voter level between a person's immigrant status and his or her support for Johnson?

Explain briefly.