In the data-based individualization framework, if a student demonstrates limited response to a validated intervention delivered with fidelity, educators use diagnostic data to determine how to best intensify the intervention. Errors in student work samples are one type of diagnostic data that educators may use to better understand students’ skill gaps. Error analysis is a process for analyzing student work samples to (a) identify common types of errors in the student’s work and (b) use this information to better align the intervention with the student’s needs. This tip sheet provides an overview of how to analyze errors in math.