The Dunning-Kruger effect is a cognitive bias that plagues a particular population of students--the unskilled. This population suffers from illusory competence, as determined by inaccurate ratings of their own ability/performance. These mistakenly high self-ratings (i.e. ''illusions of competence'') are typically explained by a metacognitive deficiency of the unskilled--they simply can't recognize their own mistakes. This work, involving more than a thousand students, nine course sections, and sampling multiple time points over a semester, established the Dunning-Kruger effect as a robust phenomenon in university-level introductory chemistry. Using a combination of graphical analyses and hierarchical linear modeling, we confirmed that low-performing students tend to overestimate their own performance while high-performing students tend to underestimate their performance. We also observed a clear difference between female and male students with regard to these miscalibrations. Lastly, we demonstrated that student miscalibrations are invariant over time, a result that has profound implications for the types of instructor feedback conventionally provided in introductory chemistry courses.