Due to the Covid-19 pandemic, we had to perform an online assessment for a large class of more than 300 students for an engineering mechanics module. We designed the online quiz with multiple choice and fill-in the blank questions, and incorporated two forms of randomness in the questions to minimize plagiarism. The students’ examination scores were generally in normal distributions, which suggested that the online quiz was challenging enough to differentiate the performance of the students. Hence, we believe that it is possible to create high quality and credible online quizzes, which would be useful for large class courses.