Multiple Choice Questions come with the correct answer. Examinees have various reasons for selecting their answer, other than knowing it to be correct. Yet MCQs are common as summative assessments in the education of Computer Science and Information Systems students. To what extent can MCQs be answered correctly without knowing the answer; and can alternatives such as constructed response questions offer more reliable assessment while maintaining objectivity and automation? This study sought to establish whether MCQs can be relied upon to assess knowledge and understanding. It presents a critical review of existing research on MCQs, then reports on an experimental study in which two objective tests were set for an introductory undergraduate course on bitmap graphics: one using MCQs, the other constructed responses, to establish whether and to what extent MCQs can be answered correctly without knowing the answer. Even though the experiment design meant that students had more learning opportunity prior to taking the constructed response test, student marks were higher in the MCQ test, and most students who excelled in the MCQ test did not do so in the constructed response test. The study concludes that students who selected the correct answer from a list of four options, did not necessarily know the correct answer. While not all subjects lend themselves to objectively testable constructive response questions, the study further indicates that MCQs by definition can overestimate student understanding. It concludes that while MCQs have a role in formative assessment, they should not be used in summative assessments. [For the complete proceedings, see ED590269.]