Concept inventories (CI) constitute a key thread in Physics Educational Research. As such, understanding the methodology and the technique of developing a good CI is essential for all physics teachers. This research aims to develop a circular-motion concept Inventory (CMCI) that is valid in the Ugandan context. To reach a consensus, we used the Delphi technique to collect the data from eleven experts in the physics discipline. These experts were asked to rank each CI item in the inventory, based on the relevant criteria, for assigning a degree of relevance for adoption on a scale ranging from one to four, one being "not relevant" and four being "highly relevant.” Because the technique does not require experts to meet face-to-face, they remained anonymous to one another. These experts are provided with structured questionnaires of CI items from the Rotational-Kinematics Inventory (RKI) and Rolling and Rotational Motion-Concept (RRMC) inventories in the first round, in order to adopt items relevant to circular-motion concepts in the Ugandan context. They agreed to use 31 CI items in the RKI and 14 CI items in the RRMC in the second round. The mean and standard deviation of expert replies were analysed by using descriptive statistics. We used the methodological principles of CI creation, in order to create eight CI items to fill in the missing sub-concepts. Therefore, a total of 53 concept items were created. In order to analyse their qualities in a psychometric analysis, these will be evaluated by using field testing and psychometric analysis. Various physics instructors will access the CMCI, because the field testing aims to gauge the level of educational efficacy in their academic and research initiatives.

In this study, we administered and evaluated circular motion concept question items with a view to developing an inventory suitable for the Ugandan context. Before administering the circular concept items, six physics experts and ten undergraduate physics students carried out the face and content validation. One hundred eighteen undergraduate students responded to the 42 circular motion concept items. The data were analysed using the classical test theory (CTT) and item response curve (IRC) analyses. We calculated the difficulty level and index of discrimination and gauged the distraction efficiency of items. The IRCs revealed insights that were not evident from those provided by the CTT. Based on the IRCs, the circular concept items are classified into three categories: efficient, moderately efficient, and inefficient. This helped us better evaluate the quality of the items and their appropriateness for the population under consideration. We ended up with 22 circular motion concept question items which we call the circular motion concept inventory (CMCI). This inventory is particularly relevant to Ugandan context and may be useful to other countries in the East African region which share similar syllabi.

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