Computational notebooks—such as Jupyter or Colab—combine text and data analysis code. They have become ubiquitous in the world of data science and exploratory data analysis. Since these notebooks present a different programming paradigm than conventional IDE-driven programming, it is plausible that debugging in computational notebooks might also be different. More specifically, since creating notebooks blends domain knowledge, statistical analysis, and programming, the ways in which notebook users find and fix errors in these different forms might be different. In this paper, we present an exploratory, observational study into how notebook users find and understand potential errors in notebooks. We presented users with notebooks pre-populated with common notebook errors—errors rooted in either the statistical data analysis, knowledge of domain concepts, or in the programming. We then analyze the strategies our study participants used to find these errors and determine how successful each strategy is at identifying errors. Our findings indicate that while the notebook programming environment is different from the environments used for traditional programming, debugging strategies remain quite similar. It is our hope that the insights presented in this paper will help both notebook tool designers and educators make changes to improve how data scientists discover errors more easily in the notebooks they write.