Race of the interviewer and the black-white test score gap

Does the race of interviewers introduce a bias in estimating the test score gap between blacks and whites in the United States? To answer this question. I use an adult sample from the General Social Survey (GSS) in which vocabulary testing involves face-to-face and one-on-one interaction between the respondent and the interviewer. I find that black respondents perform better when tested by a black interviewer as opposed to a white interviewer. For white respondents, however, the race of the interviewer does not have a significant impact on test performance. Because most black respondents are tested by white interviewers in the GSS, the test performance of black respondents is downward biased, and the black-white test score gap is overestimated.