Mechanical engineering students’ struggles with units of measure

Abstract

The correct use of units of measure is a critical and fundamental skill that is often taken for granted. The fact that units are taught in high school leads to the expectation that university freshmen master these skills. Unfortunately, faculty often observe that students struggle with units. Although the literature is limited on the nature and extent of students’ struggles with units, it is shown that all of it, without exception, points to a pervasive problem in STEM programs. This paper contributes to the literature by exploring the evolution in the performance of N=21 senior mechanical engineering students enrolled during the Fall 2019 semester in a 3-credit-hour, required course that prepares them for the NCEES Fundamentals of Engineering (FE) Exam. Students were given a unit-conversion quiz at the beginning each class session. It was corrected on the spot, with a score of either 1 or 0, followed by a discussion of the quiz. A score of 1 required a perfect solution. The performance on each quiz guided the decision on the content of future quizzes. The results show that 15 quizzes were required to get 100% of the students to push through their difficulties and achieve expertise. The paper includes the content of the quizzes, the solutions, the aggregated results for each quiz, and the nature of the mistakes. It also includes an algorithm to conduct unit conversions and a visualization scheme to use tables of unit conversions and tables of metric prefixes that were developed during the project. These greatly assisted students in overcoming their difficulties. The experiment was repeated the following semester (Spring 2020, N=27) to test the effectiveness of an algorithm and visualization scheme developed by the author during the Fall 2019 semester. The time to achieve expertise was reduced to one third (5 quizzes vs 15 for the original group), thus confirming its merit. Part of the discussion section focuses on the benefit of the Scholarship of Teaching and Learning (SoTL) movement, of which this paper is an example, and its use in the ABET-required processes of outcomes assessment and continuous improvement. The paper also includes suggestions for further research.