Pedagogical Justifications That Zero Factorial Equals One: Making Data-Driven Instructional Choices in Education

Zero factorial, defined to be one, is often counterintuitive to students but nonetheless an interesting concept to convey in a classroom environment. The challenge is to delineate the concept in a simple and effective way. In this regard, the contribution of this article is two-fold: First, it reveals and makes contribution to much simpler justifications on the notion of zero factorial to be one when compared to previous studies in the area. Second, to assess the effectiveness of the proposed justifications, an online survey has been conducted at a comprehensive university and, via its statistical analysis, data-driven instructional decision-making has been illustrated. Elaborating on the first contribution, we note that the connection of zero factorial to the definition of the gamma function provides a first-hand conceptual understanding of the concept of zero factorial. But for the purpose of teaching, it is not particularly helpful from the pedagogical point of view in early years of study, as it is quite challenging to explain the rationale behind the origin of the definite integral that defines the gamma function. In this regard two algebraic and one statistical justification are presented. The squeeze theorem plays a pivotal role in this article. To assess the effectiveness of the justifications pedagogically, an online survey was conducted at a Canadian university.