Assessment of CAD Related Items for a Concept Inventory for Engineering Graphics

Concept Inventories (CI) are designed to measure student understanding of fundamental concepts and have been used in education reform efforts for the past several decades. A CI for engineering graphics is currently being developed. The original intent of this graphics CI was to include both “modern” (i.e., CAD) and “traditional” (i.e., sketching, conventions, etc.) fundamental concepts. The first step in the development of any CI is to create open-ended problems. The incorrect results from these problems are used to determine common student misconceptions and ultimately form the distractors for the multiple choice items. In the initial round, the open-ended problems for traditional topics produced a variety of responses that could be clearly categorized from which distractors could then be readily identified. The traditional topics yielded one clearly correct answer. However, the open-ended problems for the CAD topics produced multiple responses that were difficult to interpret and categorize into discrete correct or incorrect classifications. Further, it was apparent that for each open-ended CAD item there were multiple correct solutions because optimal modeling strategies depend on design intent, CAD package used, and the desired manufacturing processes. Because the open-ended questions created by the researchers did not yield usable results, a series of multiple choice questions developed for assessment in a high school CAD competency exam were identified as potential CI items. The research team reviewed this exam identifying several promising candidate items for inclusion in the CI. These items were then tested with a pool of students with CAD knowledge. This paper presents the results from the betatesting of these CAD items and addresses their suitability for use in the engineering graphics Concept Inventory. Introduction The use of Concept Inventories has become increasingly popular as a method to measure student learning and potentially reform teaching methods. The incorrect responses reveal misconceptions which can be useful in evaluating instruction. Researchers involved in science education have used preand postassessments to measure student learning and validate the need for curriculum revision [1]. Engineering Graphics has been identified as a field in which the use of a CI could expose common misconceptions associated with graphic representation, as well as identify the fundamental concepts that contribute to the generation of those graphics. With varying curricula across institutions it can be expected that the implementation of engineering graphics will differ. The development of a standardized instrument to assess the understanding of concepts related to engineering graphics could be beneficial in streamlining or standardizing instruction across institutions and ensuring that deep-seated misconceptions are corrected. CAD instruction varies widely across universities due to instructors having different professional and educational backgrounds and the diverse CAD software packages used. For example, instructors with a manufacturing background may have a predisposition towards either additive modeling, a design process involving adding material from a base sketch or profile, or subtractive modeling, a design process involving taking material away from a generic mass until the desired object is achieved, both of which mimic manufacturing processes and would affect their CAD instruction. Figure 1a is a part modeled in CATIA using the Shaft command (commonly known as Revolve in other packages) on a simple profile. This is an example of an additive design process because it involves adding material from a base sketch. Figure 1b is part modeled in CATIA using the Pad (commonly known as extrude in other packages) and groove command on two separate sketches. Figure 1a: Part Modeled in CATIA Additive Method Figure 1b: Part Modeled in CATIA Subtractive Method Add material