We sometimes ask a final question that says something like this: "You won't be penalized for answering this question truthfully, regardless of what you answer. Are you a member of a racial/ethnic minority group YES  NO."

We often get participants to rule themselves out of the target group with this question, when they have up to then participated as if they were a member of the target group. And, indeed, we do still compensate them, just as we said we would.