Summative assessment qualifies the achievement of a student in a particular field of specialization at a given time. Questions should include a range of cognitive levels from Bloom's taxonomy and be consistent with the learning outcomes of the module in question. Furthermore, a holistic approach to assessment, such as the application of the principles of the Herrmann Whole Brain Model, needs to be used to accommodate learning style diversity. The purpose of this study was to analyse, assess and compare the summative assessment of two third year level modules in the Bachelor of Science degree programme, namely Biochemistry and Zoology as part of action research with a view to enhancing the professional development of the lecturers involved. The questions posed in summative assessments were classified in terms of Bloom's differentiation of cognitive levels and the four different learning styles determined by Herrmann. Spearman's non-parametric analysis indicated that no correlation existed in this study between cognitive level and student performance based on achievement. In addition, there was not much difference between the cognitive levels and student performance between the two disciplines. Although the students seemed to do better at application level questions, the authors need to reflect on whether the assessments were valid with respect to the learning outcomes, methods of facilitating learning, and the assessments based on cognitive levels and learning style preferences. We conclude that continuous action research must be taken to improve the formulation of learning outcomes and students' achievement of these outcomes and quality of student learning--the main aim being the successful completion of the modules.