IQ tests may be biased based on knowledge a certain group might have that another does not. Perhaps someone with an ESL (English as a Second Language) situation might not score as high on the English part of the test, but still have a higher IQ than the test shows. A Chinese Engineer, perhaps taking the test might get confused on the English definition and the way some questions are worded.

I am sure there are other examples. I'll let everyone else figure them out. I have a quiz to study for tonight.