What kind of measures do sociologists use to calculate prejudice other giving a person an implicit association test?
Essentially prejudice depends on how you divide people into "us" and "them" categories. There are various types of scales used (e.g., Likert-type scales and Bogardus social distance scale).
These sources might be helpful:
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http://en.wikipedia.org/wiki/Bogardus_Social_Distance_Scale
http://www.mortimeronline.com/study2/method.htm
http://72.14.253.104/search?q=cache:M7cqmI0mcXIJ:www.du.edu/idea/lessons/deprince1.doc+Likert+scale+prejudice&hl=en&gl=us&ct=clnk&cd=39&client=safari
I hope this helps. Thanks for asking.