To address concerns raised regarding the use of online course-based summative assessment methods, a quasi-experimental design was implemented in which students who completed a summative assessment either online or offline were compared on performance scores when using their self-reported "preferred" or "non-preferred" modes. Performance scores were found not to differ depending on whether the assessment was completed in the preferred or non-preferred mode. These findings provide preliminary support for the validity of online assessment methods. Future studies could help determine the extent to which this finding generalizes beyond the assessment procedures and type of sample used here. Suggestions for follow-up studies are offered, including exploring the validity of more complex computer-related online assessment tasks and investigating the impact of using preferred and non-preferred modes upon the "quality of the student experience". (Contains 5 notes and 2 tables.)