In higher education, the entry-level, not-for-credit courses in Developmental Education play a pivotal role for incoming degree-seeking students. Focusing specifically on Developmental Writing, at two- and four-year public and private institutions across the country, a common requirement to pass the course is a summative argumentative essay that displays critical reading, writing, and thinking skills. Within this writing genre, there are major competencies that students are required to display having learned the content: writing an argumentative thesis statement, selecting and incorporating effective evidence, and creating original, evidence-based arguments. This study tested if formative assessments (FA) used during the argumentative writing process could improve students' writing of the three major content skills. These FAs are called computer-based formative assessments (CBFAs) in this study because they were created on a computer and can be completed on any internet-enabled device. Using a mixed method intervention design that is founded in cognitive domain theory, specifically elements of evidence-centered design (ECD) and the Zone of Proximal Development (ZPD), the results show that the CBFA intervention tools positively impacted student writing. The main data analysis is a paired T-test, comparing the pre-assessment and post-assessment overall scores. Qualitative data includes writing samples and student and instructor feedback. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]