I used a range of assessment techniques in this course. Each of the projects had separate write-ups or some kind of final product (the last project required a GSA-style poster). These write-ups could be revised with new knowledge gained from later parts of the course and each had a solid grading rubric. Some of the specific in-class activities related to the projects were handed in and I commented on them, but I typically did not assign a grade. Finally, I developed a final exam (Acrobat (PDF) 811kB Jul1 05) that specifically tested their ability to achieve the over-arching goal of the course: they were given a strat column from an area they had never seen before and they had to integrate the course's knowledge to interpret the depositional environments present in the column. At the end of the course, I required students to hand in copies of all three of their projects in a portfolio, with any revisions highlighted; I have kept these portfolios in an effort to assess the evolving effectiveness of the course.
In terms of assessing whether the PBL format worked better than a non-PBL format, most of my evidence is anecdotal. When comparing the content that I covered in the non-PBL course to the new course, I found that I gave up very little. It was important to me that students use the textbook as a reference for their work and perhaps one of the most visible pieces of evidence that this was achieved was the 'textbook wear factor:' student texts were more beaten up and dog-eared than I have ever seen at the end of a course, and the books started out the semester largely untouched. I found that depth of in-class discussion was more intense and more real than I experienced in the non-PBL format and my overall satisfaction for teaching the course was much higher. I performed a Student Assessment of Learning Gains (SALG) on this course and the evidence was strong that students felt that they had learned a lot about the material in it. Finally, I have now worked with many of the students in this class on independent research projects and I found that they were better-prepared to pursue this research. I cannot completely attribute this to my PBL sed/strat course, but I do know that they made better field observations and were more critical thinkers than students I had worked with before.