The present paper focuses on in-course sample diagnostic questions relating to functions for students who choose to take a course on differential calculus, in a South African context. However, the diagnostic questions should be useful at many places worldwide. The researchers formulated learning outcomes and in-course diagnostic questions for the technical knowledge and skills required for the section on functions, in the context of differential calculus. The questions were designed to check the relevant learning outcomes that they detected for the section on functions as informed by the literature review and conceptual framework. The learning outcomes and formulation of diagnostic outcomes, although based on a number of assumptions, should improve the performance of students. © Kamla-Raj 2015 Int J Edu Sci, 8(3): 629-643 (2015)