Students are guided through a case study used to introduce the IOU inquiry process (making Inferences from Observations based on Understanding) used in Problem Based Learning (PBL). Opportunity for formative assessment of both process skills and content knowledge is provided following the first case study. Once the skills and processes are developed, students move on to a small group case study using the same process to increase the depth of understanding. Using this process, students will develop their skills in observation, inference, questioning, research, and data analysis through case studies freely available from the internet. During the process, students should develop enough depth of understanding to be successful on a traditional paper/pencil unit test in addition to the case study evaluation.