The Microbiology Concept Inventory is an assessment tool derived from the fundamental statements created by the American Society for Microbiology. This two-tier, multiple-choice question inventory requires students to choose the most correct answer for each question and provide a brief justification of their reasoning. Educators can utilize this tool to identify common misconceptions held by students and adjust curriculum to address and prevent the persistence of student misconceptions. Over the course of 5 years, the Microbiology Concept Inventory was annually administered to undergraduate students enrolled in entry-level, mid-level, and senior capstone microbiology courses at a mid-western rural university. Analysis was completed to compare course, year, majors and minors, gender, ethnicity, and cumulative GPA. Results of this study showed a significant difference in Microbiology Concept Inventory scores between students with high cumulative GPAs (3.5–4.0) and students with comparatively lower cumulative GPAs (2.5–2.99, 3.0–3.49). Results between the other demographic categories revealed statistically different scores in favor of white students, but no differences in scores between genders. The results suggest evidence of ethnic bias, but no gender bias as measured by the Microbiology Concept Inventory. Additionally, significant differences in scores across cohorts are indicative of improvements in the curricula due to prior targeted changes. Analysis of concept inventory results can guide curriculum changes for course instructors. Implementation of curriculum changes can enrich students’ academic success.