This is a story about discovering a bias that affected participation grades in my Introductory Physics for Life Sciences class. My expectation, that actively engaged students tended to talk frequently in my presence as their teaching assistant, would have erased two students' outstanding performances if not for the participation grade policies described here. The two students, Diana and Alice (pseudonyms), both appeared to be Asian American women, which prompted a quick check for possible course-wide bias in participation grades by students' gender and ethnicity. The quick check--a quantitative analysis--suggested that in-class participation by multiple different groups of Asian American women may have been undervalued on average by graduate physics teaching assistants, though this requires further analysis. My perspective of Diana's and Alice's top performances along with the informal check connects to published research on Asian American student experiences. I also present practical suggestions for physics educators, who could benefit from critically reflecting on what values and biases may be baked into their grading schemes.