Grades influence students' confidence and decisions to complete STEM degrees and pursue relevant careers. What affects students' confidence and performance in college upper-division biology laboratory courses and how relevant are evaluation methods to career success? STEM laboratory courses are an excellent model to address these issues because of the hybrid environment, combining traditional lecture course format and the practical application of knowledge. We surveyed 567 students in two upper-division laboratory molecular biology courses at a major research university to compare course-content self-assessment, students' predicted grades, and actual grades received. By analyzing students' confidence and correlating them to grades assigned by the instructor, we identified biases including student and Instructor Assistant (IA) gender, IA experience, and academic quarter. Considering the systemic effect of identified biases, a correlation (R[superscript 2] = 0.37, p < 0.01) between predicted and actual grades, and weak but statistically significant correlation (R[superscript 2] = 0.10, p < 0.01) between students' comprehensive course-content self-assessment and their predicted grade are not surprising. Our analysis suggests that students' quantifiable self-assessment, a relatively simple and data-rich resource, helps identify evaluation bias. If administered periodically throughout the course, these assessments can help mitigate biases, improve student learning, evaluation, and retention in STEM fields.