Development of a research instrument to measure student achievement requires planning and reliability and validity testing before the instrument is used to collect data. These steps are often overlooked in research studies, but when the instrument is to be used across a wider population, the inclusion of these steps is vital to address the generalizability of the results. Reliability testing ensures that the instrument measures appropriate content to the degree planned by the researcher. This study describes the development of a nationwide student-achievement and process-skills instrument that was tested for both reliability and validity. The instrument was subsequently used in a nationwide study to investigate differences in student learning for both Process-Oriented Guided Inquiry Learning (POGIL) and non-POGIL general chemistry students.